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Advisory record · GHSA-f8fg-pg57-v4j8

league/commonmark XSS: `on*` event-handler filter in `AttributesExtension` bypassed with a U+000C form feed

CVSS 6.9 MediumEPSS 0.0039 · 33rd percentile

Published by the GitHub Advisory Database at 1 Sept 2026, 20:18 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
league/commonmarkPackagist>=2.7.0, <2.9.12.9.1
Identifiers
GHSA-f8fg-pg57-v4j8 · CVE-2026-86431 · PKSA-kr3s-894t-g5w2
Weakness (CWE)
CWE-79 · CWE-86
Tags
Published
1 Sept 2026
Updated
8 Sept 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
6.9 Medium 4.0 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N CNA (VulnCheck)
  • CISA KEV Not listed.
  • EPSS 0.0039, the 33rd 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.