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Advisory record · GHSA-jjv6-8j6v-6j52

league/commonmark: Denial of service in the SmartPunct and Attributes extensions

CVSS 8.7 HighEPSS 0.0052 · 44th percentile

Published by the GitHub Advisory Database at 1 Sept 2026, 20:21 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
league/commonmarkPackagist>=1.5.0, <2.9.12.9.1
Identifiers
GHSA-jjv6-8j6v-6j52 · CVE-2026-86429 · PKSA-nv44-1b4d-6gjg
Weakness (CWE)
CWE-407 · CWE-1050
Tags
Published
1 Sept 2026
Updated
8 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Versions 2.0.0 through 2.9.0 of league/commonmark (and 1.5.0 through 2.9.0 for the Attributes extension paths) have quadratic parsing behaviour in the SmartPunct and Attributes extensions, which apply only when those extensions are explicitly registered. An unauthenticated attacker who can submit Markdown to such an application can cause excessive CPU use with a fairly small input, degrading availability without disclosing data. Upgrade to version 2.9.1 or later; if that is not possible, avoid registering these extensions for untrusted input or impose a strict maximum input length.

Written 31 Oct 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
8.7 High 4.0 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N CNA (VulnCheck)
  • CISA KEV Not listed.
  • EPSS 0.0052, the 44th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:06 UTC First seen by agentprime
  2. 31 Oct 2026, 14:06 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.