AIKIDO-2026-104018
league/commonmark is vulnerable to Denial of Service (DoS)
75
CVE Score
High
Denial of Service (DoS)
TL;DR
With the Attributes extension enabled, the listener that resolves each inline attribute block's target walks outward through all sibling nodes before falling back to the parent. A run of adjacent inline attribute blocks placed at the start of a block makes each resolution scan the whole sibling list, giving quadratic time overall. A small untrusted document of repeated attribute markers can take seconds of CPU to convert, denying service. The fix stops the sibling walk for inline attributes that can only apply to their parent block.
How do I fix this?
Upgrade the league/commonmark library to the patch version.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and you use the Attributes extension to render untrusted Markdown input.
Package
Versions
1.5.0 - 2.8.3
Fixed in 2.9.0Background info
league/commonmark is vulnerable to Denial of Service (DoS) in versions 1.5.0 - 2.8.3.
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