Find, fix and prevent vulnerabilities in your code.

Overview

activesupport is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) in number_to_delimited() in the NumberToDelimitedConverter. An attacker can cause excessive resource consumption by submitting excessively long digit strings.

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.

The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.

Let’s take the following regular expression as an example:

regex = /A(B|C+)+D/

This regular expression accomplishes the following:

• A The string must start with the letter 'A'
• (B|C+)+ The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the + matches one or more times). The + at the end of this section states that we can look for one or more matches of this section.
• D Finally, we ensure this section of the string ends with a 'D'

The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD

It most cases, it doesn't take very long for a regex engine to find a match:

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total

The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.

Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.

Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:

1. CCC
2. CC+C
3. C+CC
4. C+C+C.

The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.

From there, the number of steps the engine must use to validate a string just continues to grow.

By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.

Remediation

Upgrade activesupport to version 7.2.3.1, 8.0.4.1, 8.1.2.1 or higher.

References

• GitHub Advisory
• GitHub Commit
• GitHub Commit
• GitHub Commit
• GitHub Release
• GitHub Release
• GitHub Release

Overview

Affected versions of this package are vulnerable to Infinite loop in the AtomicReference#update function when the current value is Float::NAN. An attacker can cause indefinite busy retry loops and CPU exhaustion by supplying malicious numeric data.

Remediation

Upgrade concurrent-ruby to version 1.3.7 or higher.

References

• GitHub Advisory
• GitHub Commit

Overview

nokogiri is a gem for parsing HTML, XML, SAX, and Reader.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) in the CSS selector tokenizer in css/tokenizer.rb. An attacker can cause excessive resource consumption by supplying malicious input to CSS.xpath_for.

Workaround

This vulnerability can be mitigated by setting a global Regexp.timeout.

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.

The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.

Let’s take the following regular expression as an example:

regex = /A(B|C+)+D/

This regular expression accomplishes the following:

• A The string must start with the letter 'A'
• (B|C+)+ The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the + matches one or more times). The + at the end of this section states that we can look for one or more matches of this section.
• D Finally, we ensure this section of the string ends with a 'D'

The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD

It most cases, it doesn't take very long for a regex engine to find a match:

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total

The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.

Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.

Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:

1. CCC
2. CC+C
3. C+CC
4. C+C+C.

The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.

From there, the number of steps the engine must use to validate a string just continues to grow.

By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.

Remediation

Upgrade nokogiri to version 1.19.3 or higher.

References

• GitHub Advisory
• GitHub Commit

Overview

nokogiri is a gem for parsing HTML, XML, SAX, and Reader.

Affected versions of this package are vulnerable to Unchecked Return Value from xmlC14NExecute, used in the canonicalize methods. These return and empty string rather than an error code for invalid and incomplete XML inputs. Although this behavior is not in itself a vulnerability in the parsing functionality, it has been demonstrated to be exploitable as a signature bypass in the vulnerability described in CVE-2025-66568.

Note: This is only exploitable in the CRuby extension. JRuby is not vulnerable.

Remediation

Upgrade nokogiri to version 1.19.1 or higher.

References

• GitHub Commit
• GitHub Commit

Overview

rexml is an An XML toolkit for Ruby.

Affected versions of this package are vulnerable to Denial of Service (DoS) via the REXML gem, when parsing an XML document that has many specific characters such as whitespace character,>] and ]>.

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.

Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.

One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.

When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.

Two common types of DoS vulnerabilities:

• High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.

• Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm ws package

Remediation

Upgrade rexml to version 3.3.3 or higher.

References

• ruby-lang News

Overview

rexml is an An XML toolkit for Ruby.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) due to the usage of insecure regular expressions in CHARACTER_REFERENCES. This vulnerability can be exploited when parsing XML content containing numerous digits between &# and x...; in a hex numeric character reference (&#x...;).

By supplying specially crafted XML documents, an attacker can cause the application to consume excessive resources.

Note:

This vulnerability doesn't affect Ruby 3.2 or later.

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its original and legitimate users. There are many types of DoS attacks, ranging from trying to clog the network pipes to the system by generating a large volume of traffic from many machines (a Distributed Denial of Service - DDoS - attack) to sending crafted requests that cause a system to crash or take a disproportional amount of time to process.

The Regular expression Denial of Service (ReDoS) is a type of Denial of Service attack. Regular expressions are incredibly powerful, but they aren't very intuitive and can ultimately end up making it easy for attackers to take your site down.

Let’s take the following regular expression as an example:

regex = /A(B|C+)+D/

This regular expression accomplishes the following:

• A The string must start with the letter 'A'
• (B|C+)+ The string must then follow the letter A with either the letter 'B' or some number of occurrences of the letter 'C' (the + matches one or more times). The + at the end of this section states that we can look for one or more matches of this section.
• D Finally, we ensure this section of the string ends with a 'D'

The expression would match inputs such as ABBD, ABCCCCD, ABCBCCCD and ACCCCCD

It most cases, it doesn't take very long for a regex engine to find a match:

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCD")'
0.04s user 0.01s system 95% cpu 0.052 total

$ time node -e '/A(B|C+)+D/.test("ACCCCCCCCCCCCCCCCCCCCCCCCCCCCX")'
1.79s user 0.02s system 99% cpu 1.812 total

The entire process of testing it against a 30 characters long string takes around ~52ms. But when given an invalid string, it takes nearly two seconds to complete the test, over ten times as long as it took to test a valid string. The dramatic difference is due to the way regular expressions get evaluated.

Most Regex engines will work very similarly (with minor differences). The engine will match the first possible way to accept the current character and proceed to the next one. If it then fails to match the next one, it will backtrack and see if there was another way to digest the previous character. If it goes too far down the rabbit hole only to find out the string doesn’t match in the end, and if many characters have multiple valid regex paths, the number of backtracking steps can become very large, resulting in what is known as catastrophic backtracking.

Let's look at how our expression runs into this problem, using a shorter string: "ACCCX". While it seems fairly straightforward, there are still four different ways that the engine could match those three C's:

1. CCC
2. CC+C
3. C+CC
4. C+C+C.

The engine has to try each of those combinations to see if any of them potentially match against the expression. When you combine that with the other steps the engine must take, we can use RegEx 101 debugger to see the engine has to take a total of 38 steps before it can determine the string doesn't match.

From there, the number of steps the engine must use to validate a string just continues to grow.

By the time the string includes 14 C's, the engine has to take over 65,000 steps just to see if the string is valid. These extreme situations can cause them to work very slowly (exponentially related to input size, as shown above), allowing an attacker to exploit this and can cause the service to excessively consume CPU, resulting in a Denial of Service.

Remediation

Upgrade rexml to version 3.3.9 or higher.

References

• GitHub Commit

Overview

rexml is an An XML toolkit for Ruby.

Affected versions of this package are vulnerable to Uncontrolled Resource Consumption ('Resource Exhaustion') via the SAX2 or pull parser API. An attacker can cause the application to consume excessive resources leading to a denial of service by submitting specially crafted XML documents that exploit entity expansions.

PoC

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE member [
  <!ENTITY a "&b;&b;&b;&b;&b;&b;&b;&b;&b;&b;">
  <!ENTITY b "&c;&c;&c;&c;&c;&c;&c;&c;&c;&c;">
  <!ENTITY c "&d;&d;&d;&d;&d;&d;&d;&d;&d;&d;">
  <!ENTITY d "&e;&e;&e;&e;&e;&e;&e;&e;&e;&e;">
  <!ENTITY e "&f;&f;&f;&f;&f;&f;&f;&f;&f;&f;">
  <!ENTITY f "&g;&g;&g;&g;&g;&g;&g;&g;&g;&g;">
  <!ENTITY g "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx">
]>
<member>
&a;
</member>

Remediation

Upgrade rexml to version 3.3.3 or higher.

References

• GitHub Commit
• GitHub Release Notes
• Security Advisory
• Security Advisory

Overview

nokogiri is a gem for parsing HTML, XML, SAX, and Reader.

Affected versions of this package are vulnerable to Use After Free via the xmlTextReader module. An attacker can cause denial of service by processing crafted XML documents with DTD validation and XInclude expansion enabled.

Remediation

Upgrade nokogiri to version 1.15.6, 1.16.2 or higher.

References

• GitHub Commit
• GitHub PR
• Gitlab Commit
• Gitlab Issue
• Gitlab Release

Overview

nokogiri is a gem for parsing HTML, XML, SAX, and Reader.

Affected versions of this package are vulnerable to Incorrect Type Conversion or Cast in the protected initialize_copy_with_args copy helper behind Node#dup and #clone, which unwraps its source argument as an xmlNode without a type check. The process crashes on an out-of-bounds memory read when application code calls that method with a non-Node argument, such as a Namespace, whose memory is then read as an xmlNs. Triggering it requires the application itself to invoke the protected internal method with an incompatible type, so it is not reachable through the public API or by untrusted input.

Remediation

Upgrade nokogiri to version 1.19.4 or higher.

References

• GitHub Advisory
• GitHub Commit
• GitHub Release

Overview

activesupport is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework.

Affected versions of this package are vulnerable to Cross-site Scripting (XSS) via the @html_unsafe flag used by the SafeBuffer#% function. An attacker can inject scripts by providing untrusted arguments to the formatting operation after the buffer has been mutated in place, which mayb cause the result to be incorrectly marked as safe and bypass automatic escaping.

Details

Cross-site scripting (or XSS) is a code vulnerability that occurs when an attacker “injects” a malicious script into an otherwise trusted website. The injected script gets downloaded and executed by the end user’s browser when the user interacts with the compromised website.

This is done by escaping the context of the web application; the web application then delivers that data to its users along with other trusted dynamic content, without validating it. The browser unknowingly executes malicious script on the client side (through client-side languages; usually JavaScript or HTML) in order to perform actions that are otherwise typically blocked by the browser’s Same Origin Policy.

Injecting malicious code is the most prevalent manner by which XSS is exploited; for this reason, escaping characters in order to prevent this manipulation is the top method for securing code against this vulnerability.

Escaping means that the application is coded to mark key characters, and particularly key characters included in user input, to prevent those characters from being interpreted in a dangerous context. For example, in HTML, < can be coded as &lt; and > can be coded as &gt; in order to be interpreted and displayed as themselves in text, while within the code itself, they are used for HTML tags. If malicious content is injected into an application that escapes special characters and that malicious content uses < and > as HTML tags, those characters are nonetheless not interpreted as HTML tags by the browser if they’ve been correctly escaped in the application code and in this way the attempted attack is diverted.

The most prominent use of XSS is to steal cookies (source: OWASP HttpOnly) and hijack user sessions, but XSS exploits have been used to expose sensitive information, enable access to privileged services and functionality and deliver malware.

Types of attacks

There are a few methods by which XSS can be manipulated:

Affected environments

The following environments are susceptible to an XSS attack:

• Web servers
• Application servers
• Web application environments

How to prevent

This section describes the top best practices designed to specifically protect your code:

• Sanitize data input in an HTTP request before reflecting it back, ensuring all data is validated, filtered or escaped before echoing anything back to the user, such as the values of query parameters during searches.
• Convert special characters such as ?, &, /, <, > and spaces to their respective HTML or URL encoded equivalents.
• Give users the option to disable client-side scripts.
• Redirect invalid requests.
• Detect simultaneous logins, including those from two separate IP addresses, and invalidate those sessions.
• Use and enforce a Content Security Policy (source: Wikipedia) to disable any features that might be manipulated for an XSS attack.
• Read the documentation for any of the libraries referenced in your code to understand which elements allow for embedded HTML.

Remediation

Upgrade activesupport to version 7.2.3.1, 8.0.4.1, 8.1.2.1 or higher.

References

• GitHub Advisory
• GitHub Commit
• GitHub Commit
• GitHub Commit
• GitHub Release
• GitHub Release
• GitHub Release

Overview

rexml is an An XML toolkit for Ruby.

Affected versions of this package are vulnerable to Denial of Service (DoS) through the XML parsing process. An attacker can cause a denial of service by sending specially crafted XML documents that contain many specific characters such as <, 0, and %>.

This vulnerability is exploitable if the application is configured to parse untrusted XML documents.

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.

Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.

One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.

When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.

Two common types of DoS vulnerabilities:

• High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.

• Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm ws package

Remediation

Upgrade rexml to version 3.3.2 or higher.

References

• GitHub Commit
• GitHub Release
• PoC
• Security Advisory

Overview

rexml is an An XML toolkit for Ruby.

Affected versions of this package are vulnerable to Uncontrolled Resource Consumption ('Resource Exhaustion') when parsing an XML that has many <s in an attribute value. An attacker can cause a denial of service by exploiting this behavior.

Workaround

This vulnerability can be mitigated by not parsing untrusted XMLs.

Remediation

Upgrade rexml to version 3.2.7 or higher.

References

• Advisory
• GitHub Commit
• PoC

Overview

Affected versions of this package are vulnerable to Improper Locking in the release_write_lock() and release_read_lock() functions. An attacker can disrupt synchronization guarantees and exploit data races or cause denial of service by invoking these functions from unauthorized threads or without holding the appropriate lock.

Remediation

Upgrade concurrent-ruby to version 1.3.7 or higher.

References

• GitHub Advisory
• GitHub Commit

Overview

Affected versions of this package are vulnerable to Wrap-around Error in ReentrantReadWriteLock that causes incorrect write locks. An attacker can cause a thread to incorrectly obtain a write lock without exclusivity by repeatedly acquiring the read lock 32,768 times, which overflows the internal counter and bypasses the global writer state. This allows other threads to continue acquiring read locks concurrently, leading to data races and inconsistent reads of shared mutable state.

Remediation

Upgrade concurrent-ruby to version 1.3.7 or higher.

References

• GitHub Advisory
• GitHub Commit

Overview

nokogiri is a gem for parsing HTML, XML, SAX, and Reader.

Affected versions of this package are vulnerable to Use After Free through the numbers.c component. An attacker can cause memory corruption or execute arbitrary code by exploiting nested XPath evaluations where an XPath context node is modified but not restored.

Remediation

Upgrade nokogiri to version 1.18.4 or higher.

References

• GitHub Commit
• Gitlab Commit
• Gitlab Issue

Overview

nokogiri is a gem for parsing HTML, XML, SAX, and Reader.

Affected versions of this package are vulnerable to Use After Free through the xsltGetInheritedNsList process. An attacker can manipulate memory and potentially execute arbitrary code by excluding result prefixes.

Remediation

Upgrade nokogiri to version 1.18.4 or higher.

References

• GitHub Commit
• Gitlab Commit
• Gitlab Issue

Overview

activesupport is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework.

Affected versions of this package are vulnerable to Information Exposure. The ImpactActiveSupport::EncryptedFile method writes contents that will be encrypted to a temporary file. The temporary file’s permissions are defaulted to the user’s current umask settings, meaning that it’s possible for other users on the same system to read the contents of the temporary file.

Note:

Attackers that have access to the file system could possibly read the contents of this temporary file while a user is editing it.

Workaround

Users can set the umask to be more restrictive: ruby$ umask 0077

Remediation

Upgrade activesupport to version 6.1.7.5, 7.0.7.1 or higher.

References

• GitHub Commit
• GitHub Release
• Vulnerability Advisory