How severe is GHSA-x6m6-5hrf-fh6r?

GHSA-x6m6-5hrf-fh6r has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-x6m6-5hrf-fh6r?

GHSA-x6m6-5hrf-fh6r affects the following packages: markdown-it-toc-and-anchor (npm). Ecosystems affected: npm.

How do I fix GHSA-x6m6-5hrf-fh6r?

Update markdown-it-toc-and-anchor to 4.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-x6m6-5hrf-fh6r is resolved across your whole dependency graph.

How do I detect GHSA-x6m6-5hrf-fh6r in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for markdown-it-toc-and-anchor, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-x6m6-5hrf-fh6r if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is GHSA-x6m6-5hrf-fh6r actively exploited in the wild?

No public exploit code has been indexed for GHSA-x6m6-5hrf-fh6r yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was GHSA-x6m6-5hrf-fh6r published, and has it been updated?

GHSA-x6m6-5hrf-fh6r was published on September 1, 2020 and was last updated on December 7, 2023. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

HIGH severity

Denial of Service in markdown-it-toc-and-anchorGHSA-x6m6-5hrf-fh6r

HIGH

GHSA-x6m6-5hrf-fh6r is a high-severity (CVSS 7.5) vulnerability in markdown-it-toc-and-anchor. A fix is available for markdown-it-toc-and-anchor — see the affected versions and patch details below.

Published

Sep 1, 2020

Updated

Dec 7, 2023

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Dec 7, 2023 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

66other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

markdown-it-toc-and-anchornpm

50Kdownloads / week

Description

All versions of markdown-it-toc-and-anchor are vulnerable to Denial of Service. Parsing markdown containing **text**+\n@[toc] causes the application to enter and infinite loop.

Recommendation

No fix is currently available. Consider using an alternative module until a fix is made available.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`markdown-it-toc-and-anchor`	all versions	4.2.0`npm install markdown-it-toc-and-anchor@4.2.0`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for markdown-it-toc-and-anchor, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update markdown-it-toc-and-anchor to 4.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-x6m6-5hrf-fh6r is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

All versions of `markdown-it-toc-and-anchor` are vulnerable to Denial of Service. Parsing markdown containing `**text**+\n@[toc]` causes the application to enter and infinite loop. ## Recommendation No fix is currently available. Consider using an alternative module until a fix is made available.

O3 Security · Impact-Aware SCA

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