Find, fix and prevent vulnerabilities in your code.

Overview

rubyzip is a ruby module for reading and writing zip files.

Affected versions of this package are vulnerable to Denial of Service (DoS). It is possible for a crafted ZIP file to bypass application checks on ZIP entry sizes because data about the uncompressed size can be spoofed. This allows attackers to cause a denial of service through maximum disk consumption. By default, the validate_entry_sizes option should be set to true, so that callers can trust an entry's reported size when using extract.

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 rubyzip to version 1.3.0 or higher.

References

• GitHub PR

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 Deserialization of Untrusted Data via the MemCacheStore and RedisCacheStore. when untrusted user input is written to the cache store using the raw: true parameter, re-reading the result from the cache can evaluate the user input as a Marshalled object instead of plain text.

Remediation

Upgrade activesupport to version 5.2.4.3, 6.0.3.1 or higher.

References

• CVE-2020-8165 Exploit
• GitHub Commit
• Google Group Forum
• masahiro331 PoC

Overview

cocoapods-downloader is an A small library for downloading files from remotes in a folder.

Affected versions of this package are vulnerable to Command Injection via git argument injection. When calling the Pod::Downloader.preprocess_options function and using git, both the git and branch parameters are passed to the git ls-remote subcommand in a way that additional flags can be set. The additional flags can be used to perform a command injection.

PoC

require 'cocoapods-downloader'

options = { :git => '--upload-pack=touch ./HELLO1;', :branch => 'foo'}
options = Pod::Downloader.preprocess_options(options)

# ls -la

Remediation

Upgrade cocoapods-downloader to version 1.6.0, 1.6.3 or higher.

References

• GitHub PR
• GitHub PR

Overview

cocoapods-downloader is an A small library for downloading files from remotes in a folder.

Affected versions of this package are vulnerable to Command Injection via hg argument injection. When calling the download function (when using hg), the url (and/or revision, tag, branch) is passed to the hg clone command in a way that additional flags can be set. The additional flags can be used to perform a command injection.

PoC

require 'cocoapods-downloader'

options = { :hg => '--config=alias.clone=!touch ./HELLO2;'}
downloader = Pod::Downloader.for_target("./", options)
downloader.download

options = { :hg => 'foo/bar', :revision => '--config=alias.clone=!touch ./HELLO3;'}
downloader = Pod::Downloader.for_target("./", options)
downloader.download


# ls -la

Remediation

Upgrade cocoapods-downloader to version 1.6.2 or higher.

References

• GitHub PR

Overview

Affected versions of this package are vulnerable to Deserialization of Untrusted Data due to the usage of JSON.load, which is considered unsafe when used with untrusted input.

Remediation

Upgrade jmespath to version 1.6.1 or higher.

References

• GitHub Commit
• GitHub PR

Overview

addressable is an is an alternative implementation to the URI implementation that is part of Ruby's standard library.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) within the URI template implementation. A maliciously crafted template may result in uncontrolled resource consumption.

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 addressable to version 2.8.0 or higher.

References

• GitHub Commit
• RedHat Bugzilla Bug

Overview

mini_magick is a ruby wrapper for ImageMagick or GraphicsMagick command line.

Affected versions of this package are vulnerable to Remote Code Execution (RCE). A fetched remote image filename can cause remote command execution due to Image.open input being directly passed to Kernel#open, which accepts a | character followed by a command.

Remediation

Upgrade mini_magick to version 4.9.4 or higher.

References

• GitHub Commit
• GitHub Release
• PoC

Overview

Affected versions of this package are vulnerable to Directory Traversal. TZInfo::Timezone.get fails to validate time zone identifiers correctly, allowing a new line character within the identifier. With Ruby version 1.9.3 and later, TZInfo::Timezone.get can be made to load unintended files with require, executing them within the Ruby process.

This could be exploited in, for example, a Ruby on Rails application using a vulnerable version of tzinfo, that allows file uploads and has a time zone selector that accepts arbitrary time zone identifiers.

Details

A Directory Traversal attack (also known as path traversal) aims to access files and directories that are stored outside the intended folder. By manipulating files with "dot-dot-slash (../)" sequences and its variations, or by using absolute file paths, it may be possible to access arbitrary files and directories stored on file system, including application source code, configuration, and other critical system files.

Directory Traversal vulnerabilities can be generally divided into two types:

• Information Disclosure: Allows the attacker to gain information about the folder structure or read the contents of sensitive files on the system.

st is a module for serving static files on web pages, and contains a vulnerability of this type. In our example, we will serve files from the public route.

If an attacker requests the following URL from our server, it will in turn leak the sensitive private key of the root user.

curl http://localhost:8080/public/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/root/.ssh/id_rsa

Note %2e is the URL encoded version of . (dot).

• Writing arbitrary files: Allows the attacker to create or replace existing files. This type of vulnerability is also known as Zip-Slip.

One way to achieve this is by using a malicious zip archive that holds path traversal filenames. When each filename in the zip archive gets concatenated to the target extraction folder, without validation, the final path ends up outside of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicious file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:

2018-04-15 22:04:29 .....           19           19  good.txt
2018-04-15 22:04:42 .....           20           20  ../../../../../../root/.ssh/authorized_keys

Remediation

Upgrade tzinfo to version 0.3.61, 1.2.10 or higher.

References

• GitHub 0.3.61 Release
• GitHub 1.2.10 Release
• GitHub Commit

Overview

faraday_middleware is a middleware for Faraday.

Affected versions of the package are vulnerable to Arbitrary Code Injection via the YAML.load() function.

Remediation

Upgrade faraday_middleware to version 0.12.0 or higher.

References

• Aaron Patterson's Blog
• GitHub Issue
• GitHub Commit

Overview

rubyzip is a ruby module for reading and writing zip files.

Affected versions of the package are vulnerable to Arbitrary File Write via Archive Extraction (AKA "Zip Slip").

It is exploited using a specially crafted zip archive, that holds path traversal filenames. When exploited, a filename in a malicious archive is concatenated to the target extraction directory, which results in the final path ending up outside of the target folder. For instance, a zip may hold a file with a "../../file.exe" location and thus break out of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicous file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:

+2018-04-15 22:04:29 ..... 19 19 good.txt

+2018-04-15 22:04:42 ..... 20 20 ../../../../../../root/.ssh/authorized_keys

NOTE This vulnerability is due to a partial fix in CVE-2017-5946

Remediation

Upgrade rubyzip to version 1.2.2 or higher.

References

• https://github.com/rubyzip/rubyzip/commit/d07b13a6cf0a413e010c48879aebd9576bfb5f68
• https://github.com/rubyzip/rubyzip/issues/369
• https://github.com/rubyzip/rubyzip/pull/371
• https://github.com/rubyzip/rubyzip/pull/376