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Medium, CVSS 5.3amended

Showdown vulnerable to Regular Expression Denial of Service (ReDoS) in link/anchor parsing

CVE-2024-1899GHSA-rmmh-p597-ppvv

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.

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Affected packages

  • npm showdown

    Affected
    <= 2.1.0
    Fixed in
    no fixed version recorded

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
EPSS
  • CVE-2024-1899: 0.81% estimated exploitation activity in the next 30 days; percentile 56.84 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Showdownjs, versions <= 2.1.0, anchors subparser used to parse links has a nested regular expression which can lead to denial of service conditions given malicious input.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-rmmh-p597-ppvv

  2. Revision 1 · created ·

    Published from osv record GHSA-rmmh-p597-ppvv

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2024-1899

Advisory: Showdown vulnerable to Regular Expression Denial of Service (ReDoS) in link/anchor parsing
IDs: CVE-2024-1899, GHSA-rmmh-p597-ppvv
Record: https://patchnext.com/advisories/cve-2024-1899 (revision 2, source checked 26 Oct 2026, 12:48 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
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 showdown: affected <= 2.1.0

## Suggested inspection (read-only)
- `npm ls showdown --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 showdown.
- 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-rmmh-p597-ppvv (OSV record GHSA-rmmh-p597-ppvv lists affected ranges: npm showdown >=0 <=2.1.0)
- Verified: https://github.com/advisories/GHSA-rmmh-p597-ppvv (GitHub-reviewed advisory GHSA-rmmh-p597-ppvv lists affected ranges: npm showdown >=0 <=2.1.0)

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