GHSA-C2PC-G5QF-RFRF

Workarounds

If you cannot upgrade, you may be able to mitigate the issues by:

• Setting very low memory_limit and max_execution_time PHP configurations to prevent runaway resource usage
• Implementing rate-limiting, bot protection, or other approaches to reduce the risk of simultaneous bad requests hitting your site
• Limiting the size of inputs fed into this library (specifically the max length of each line)
• Limiting the use of this library to trusted users

References

Most of these issues were discovered in other Markdown parsers. You can read more about them here:

• https://github.com/commonmark/commonmark.js/issues/129
• https://github.com/commonmark/commonmark.js/issues/157
• https://github.com/commonmark/commonmark.js/issues/172
• https://github.com/github/cmark-gfm/security/advisories/GHSA-r572-jvj2-3m8p
• https://github.com/github/cmark-gfm/security/advisories/GHSA-24f7-9frr-5h2r
• https://github.com/github/cmark-gfm/security/advisories/GHSA-29g3-96g3-jg6c
• https://github.com/github/cmark-gfm/security/advisories/GHSA-r8vr-c48j-fcc5
• https://github.com/github/cmark-gfm/security/advisories/GHSA-w4qg-3vf7-m9x5
• https://github.com/github/cmark-gfm/security/advisories/GHSA-66g8-4hjf-77xh

For general information about this type of issue:

• https://en.wikipedia.org/wiki/Time_complexity
• https://cwe.mitre.org/data/definitions/407.html

Several polynomial time complexity issues in league/commonmark may lead to unbounded resource exhaustion and subsequent denial of service.

Malicious users could trigger that inefficient code with carefully crafted Markdown inputs that are specifically designed to ensure the worst-case performance is reached. Sending multiple such requests in parallel could tie up all available CPU resources and/or PHP-FPM processes, leading to denial of service for legitimate users.

GHSA-C2PC-G5QF-RFRF has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.6.0); upgrading removes the vulnerable code path.

Kodem intelligence

These vulnerabilities have been patched in version 2.6.0. All users on older versions are highly encouraged to upgrade as soon as possible.

1. What is GHSA-C2PC-G5QF-RFRF? GHSA-C2PC-G5QF-RFRF is a high-severity security vulnerability in league/commonmark (composer), affecting versions < 2.6.0. It is fixed in 2.6.0.
2. How severe is GHSA-C2PC-G5QF-RFRF? GHSA-C2PC-G5QF-RFRF has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of league/commonmark are affected by GHSA-C2PC-G5QF-RFRF? league/commonmark (composer) versions < 2.6.0 is affected.
4. Is there a fix for GHSA-C2PC-G5QF-RFRF? Yes. GHSA-C2PC-G5QF-RFRF is fixed in 2.6.0. Upgrade to this version or later.
5. Is GHSA-C2PC-G5QF-RFRF exploitable, and should I be worried? Whether GHSA-C2PC-G5QF-RFRF is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether GHSA-C2PC-G5QF-RFRF is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix GHSA-C2PC-G5QF-RFRF? Upgrade league/commonmark to 2.6.0 or later.

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