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CVE-2026-59930: Mistune toc / TableOfContents directive: heading IDs use predictable `toc_N` numbering with no slugification, allowing collision with attacker-controlled `id="toc_N"` content

mediumCVSS 4.3CVE-2026-59930

CSIRTS triage

vendor: Mistuneproduct: MistuneOther
What
The TableOfContents directive allows for predictable heading IDs that can collide with attacker-controlled content.
Who is affected
Users of Mistune are affected by this vulnerability.
Urgency
Remediation is necessary as it poses a medium severity risk.
Action
Consider updating to a patched version of Mistune when available.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source
Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity
medium — CVSS 4.3
Published
2026-07-02
Exploitation
Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-59930

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2026-59930coverage & exploitation statusNVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Mistune toc /

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

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