1. What is this vulnerability and why does it matter?

This vulnerability, identified as CVE-2022-29181, exists in Nokogiri, an open-source XML and HTML library for Ruby. The flaw stems from a lack of proper type-checking for inputs processed by its XML and HTML4 SAX parsers. This allows an attacker to provide specially crafted untrusted inputs, which can lead to illegal memory access errors, resulting in a segmentation fault (segfault) or the ability to read from unrelated memory locations. This vulnerability is critical because it can cause a denial of service (via segfault) in applications relying on Nokogiri to process untrusted data, or potentially lead to information disclosure by allowing unauthorized reading of memory, compromising data confidentiality.

2. What are the CVSS score, severity level, and disclosure details?

The CVSS score for this vulnerability is 8.2. Based on this score, the severity level is classified as High. The vulnerability was publicly disclosed on 2022-05-20 00:00:00, with its last modification date being 2025-05-27 14:51:01.

3. Which products, vendors, systems, and versions are affected?

• Product: Nokogiri (an open source XML and HTML library)
• Vendors: The Nokogiri project maintainers.
• Systems: Any application or system that utilizes the Nokogiri library within a Ruby environment.
• Versions: All versions of Nokogiri prior to 1.13.6 are affected.

4. What is the technical root cause and attack vector?

The technical root cause of this vulnerability is improper input validation, specifically the lack of type-checking for inputs passed to Nokogiri's XML and HTML4 SAX parsers. This allows malformed or unexpected data types to be processed in a way that leads to memory safety issues. The primary attack vector involves supplying specially crafted untrusted inputs to applications that use vulnerable versions of Nokogiri for parsing XML or HTML content.

5. How can this vulnerability be exploited?

This vulnerability can be exploited by an attacker who can provide malicious, specially crafted input to an application that uses a vulnerable version of the Nokogiri library. When the application attempts to parse this untrusted input using Nokogiri's XML or HTML4 SAX parsers, the lack of type-checking leads to illegal memory access errors. This can manifest as a denial of service (DoS) by causing the application to crash due to a segmentation fault (segfault), or potentially allow the attacker to read sensitive data from unrelated memory regions, leading to information disclosure.

6. What mitigation steps and patches are available?

• Patch: The primary mitigation is to upgrade Nokogiri to version 1.13.6 or later, as this version contains a patch that addresses the issue.
• Workaround: If immediate patching is not feasible, a workaround involves ensuring that any untrusted input processed by Nokogiri's SAX parsers is explicitly converted to a String data type. This can be achieved by calling the #to_s method or an equivalent method on the input before passing it to Nokogiri.

7. How can vulnerable systems be detected?

Vulnerable systems can be detected by identifying the version of the Nokogiri gem installed in Ruby applications. Any application utilizing Nokogiri versions earlier than 1.13.6 is considered vulnerable to CVE-2022-29181. System administrators and developers should check their Gemfile.lock or installed gem list to determine the current version.

10. What public intelligence references and advisories exist?

• CVE Identifier: CVE-2022-29181
• Common Weakness Enumeration (CWE):
  • CWE-241: Improper Handling of Undefined Values
  • CWE-843: Access of Uninitialized Pointer
• Project Advisories: The official Nokogiri project releases typically include advisories for security fixes, which would reference the patch in version 1.13.6.

11. What is the risk assessment and urgency level?

The risk level for CVE-2022-29181 is assessed as High, primarily due to its CVSS score of 8.2. The potential impacts include denial of service, which can severely disrupt application availability, and information disclosure through illegal memory reads, which can compromise sensitive data. The urgency level for addressing this vulnerability is also High, especially for applications that process external or untrusted XML/HTML inputs. Organizations are strongly advised to apply the available patch (upgrade to Nokogiri 1.13.6 or later) or implement the recommended workaround immediately to prevent potential exploitation and mitigate associated risks.