GHSA-5v2h-r2cx-5xgj
HIGHInefficient Regular Expression Complexity in marked
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
markedReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
Impact
What kind of vulnerability is it?
Denial of service.
The regular expression inline.reflinkSearch may cause catastrophic backtracking against some strings.
PoC is the following.
import * as marked from 'marked';
console.log(marked.parse(`[x]: x
\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](`));
Who is impacted?
Anyone who runs untrusted markdown through marked and does not use a worker with a time limit.
Patches
Has the problem been patched?
Yes
What versions should users upgrade to?
4.0.10
Workarounds
Is there a way for users to fix or remediate the vulnerability without upgrading?
Do not run untrusted markdown through marked or run marked on a worker thread and set a reasonable time limit to prevent draining resources.
References
Are there any links users can visit to find out more?
- https://marked.js.org/using_advanced#workers
- https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS
For more information
If you have any questions or comments about this advisory:
- Open an issue in marked
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | marked | all versions | 4.0.10 |
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 dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for marked. 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.
Fix
Update marked to 4.0.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5v2h-r2cx-5xgj is resolved across your whole dependency graph.
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.
How O3 protects you
O3 pinpoints whether GHSA-5v2h-r2cx-5xgj 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 GHSA-5v2h-r2cx-5xgj. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-5v2h-r2cx-5xgj in your dependencies?
O3 detects GHSA-5v2h-r2cx-5xgj across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.