Regular Expression Denial of Service in markdown
What to do
Vendor response not established. Follow the primary source's mitigation guidance and check back for a fix.
This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.
Affected packages
npm markdown
- Affected
- every version
- Fixed in
- no fixed version recorded
Sources
- Open Source Vulnerabilities (OSV.dev), including the GitHub Advisory Database
OSV record GHSA-wx77-rp39-c6vg lists affected ranges: npm markdown >=0.0.0
VerifiedObserved Structured OSV record; GitHub-reviewed advisory.
- GitHub Advisory Database and maintainer security advisories on GitHub
GitHub-reviewed advisory GHSA-wx77-rp39-c6vg lists affected ranges: npm markdown >=0.0.0
VerifiedObserved Structured GitHub Advisory Database record (type=reviewed) from the GitHub REST API.
Severity and exploitation
- Exploitation
- No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
- CVSS
- not scored
- EPSS
- No dated EPSS signal available.
Source description
As published by the source; long descriptions are shortened.
All versions of markdown are vulnerable to Regular Expression Denial of Service (ReDoS). The markdown.toHTML() function has significantly degraded performance when parsing long strings containing underscores. This may lead to Denial of Service if the parser accepts user input. Recommendation No fix is currently available. Consider using an alternative package until a fix is made available.
Dates and revisions
- Published by the source
- Last modified by the source
- Source last checked
- Revision 2 · amended ·
Amended from ghsa record GHSA-wx77-rp39-c6vg
- Revision 1 · created ·
Published from osv record GHSA-wx77-rp39-c6vg
Agent brief
Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.
# Patch Next advisory brief: GHSA-wx77-rp39-c6vg Advisory: Regular Expression Denial of Service in markdown IDs: GHSA-wx77-rp39-c6vg Record: https://patchnext.com/advisories/ghsa-wx77-rp39-c6vg (revision 2, source checked 26 Oct 2026, 12:15 UTC) Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected. Severity: Unrated Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV. Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed. ## Affected components - npm markdown: affected every version ## Suggested inspection (read-only) - `npm ls markdown --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`. ## Supported action No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything. ## Required regression checks - Run the test suite and a production build. - Exercise the features that depend on markdown. - Repeat the inspection and confirm that only fixed versions remain installed. ## Rollback considerations - Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward. ## Unresolved questions - Which deployments run an affected version? - Exploitation status can change. Check again before lowering the priority. - Mark the work resolved only after the fixed version is verified in production. ## Sources - Verified: https://osv.dev/vulnerability/GHSA-wx77-rp39-c6vg (OSV record GHSA-wx77-rp39-c6vg lists affected ranges: npm markdown >=0.0.0) - Verified: https://github.com/advisories/GHSA-wx77-rp39-c6vg (GitHub-reviewed advisory GHSA-wx77-rp39-c6vg lists affected ranges: npm markdown >=0.0.0) Commands are suggestions: review each one before running it.
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