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CVE-2021-23341

HIGH

CVE-2021-23341 is a high-severity (CVSS 7.5) vulnerability in prismjs. 4 public exploit references exist, so weaponization risk is real. O3 Security confirms whether CVE-2021-23341 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

Denial of service in prismjs

Also known asGHSA-h4hr-7fg3-h35w
Published
Feb 18, 2021
Updated
Jul 9, 2026
Affected
1 pkg
Patched
1 / 1
Exploits
4 known

Blast Radius

1 pkg affected

Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.

prismjsnpm
26.8Mdownloads / week

Description

The package prismjs before 1.23.0 are vulnerable to Regular Expression Denial of Service (ReDoS) via the prism-asciidoc, prism-rest, prism-tap and prism-eiffel components.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmprismjsall versions1.23.0
Exploits & PoCs
4

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Detection & mitigation playbook

Open-source dependency
  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for prismjs. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

  2. Fix

    Update prismjs to 1.23.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-23341 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 pinpoints whether CVE-2021-23341 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2021-23341. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

The package prismjs before 1.23.0 are vulnerable to Regular Expression Denial of Service (ReDoS) via the prism-asciidoc, prism-rest, prism-tap and prism-eiffel components.
O3 Security · Impact-Aware SCA

Is CVE-2021-23341 in your dependencies?

O3 detects CVE-2021-23341 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.