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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 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

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
• Security Advisory

Overview

rexml is an An XML toolkit for Ruby.

Affected versions of this package are vulnerable to Uncontrolled Resource Consumption 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