league/commonmark's quadratic complexity bugs may lead to a denial of service

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Impact 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. Patches These vulnerabilities have been patched in version 2.6.0. All users on older versions are highly encouraged to upgrade as soon as possible. Workarounds If you cannot upgrade, you may be able to mitigate the issues by: - Setting very low memorylimit and maxexecutiontime 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…

Published by the source

9 Dec 2024, 20:42 UTC

Last modified by the source

9 Dec 2024, 20:42 UTC

Source last checked

26 Oct 2026, 14:29 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-c2pc-g5qf-rfrf

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# Patch Next advisory brief: GHSA-c2pc-g5qf-rfrf

Advisory: league/commonmark's quadratic complexity bugs may lead to a denial of service
IDs: GHSA-c2pc-g5qf-rfrf
Record: https://patchnext.com/advisories/ghsa-c2pc-g5qf-rfrf (revision 1, source checked 26 Oct 2026, 14:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: league/commonmark 2.6.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist league/commonmark: affected < 2.6.0; fixed in 2.6.0

## Suggested inspection (read-only)
- Packagist league/commonmark: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on league/commonmark.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-c2pc-g5qf-rfrf (GitHub-reviewed advisory GHSA-c2pc-g5qf-rfrf lists affected ranges: Packagist league/commonmark >=0 <2.6.0)

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