Inefficient Algorithmic Complexity Affecting league/commonmark package, versions >=1.5.0, <2.9.0
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-PHP-LEAGUECOMMONMARK-18600654
- published9 Aug 2026
- disclosed6 Aug 2026
- creditUnknown
Introduced: 6 Aug 2026
CVE-2026-86433 (opens in a new tab)How to fix?
Upgrade league/commonmark to version 2.9.0 or higher.
Overview
league/commonmark is a PHP-based Markdown parser which supports the full CommonMark spec. It is based on the CommonMark JS reference implementation.
Affected versions of this package are vulnerable to Inefficient Algorithmic Complexity due to inefficient processing in the AttributesListener::findTargetAndDirection function when handling adjacent inline attribute blocks with the Attributes extension enabled. An attacker can cause excessive CPU consumption by submitting specially crafted input containing a large number of adjacent attribute blocks, leading to significant delays in processing.
Workaround
This vulnerability can be mitigated by disabling the Attributes extension for untrusted input or by imposing a strict maximum input length before conversion.