GHSA-mh29-5h37-fv8m is a medium-severity (CVSS 5.3) CWE-1321 vulnerability in js-yaml. A fix is available for js-yaml — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-mh29-5h37-fv8m.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
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.
js-yamlnpmDescription
Impact
In js-yaml 4.1.0, 4.0.0, and 3.14.1 and below, it's possible for an attacker to modify the prototype of the result of a parsed yaml document via prototype pollution (__proto__). All users who parse untrusted yaml documents may be impacted.
Patches
Problem is patched in js-yaml 4.1.1 and 3.14.2.
Workarounds
You can protect against this kind of attack on the server by using node --disable-proto=delete or deno (in Deno, pollution protection is on by default).
References
https://cheatsheetseries.owasp.org/cheatsheets/Prototype_Pollution_Prevention_Cheat_Sheet.html
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | js-yaml | ≥ 4.0.0&&< 4.1.1 | 4.1.1npm install js-yaml@4.1.1 |
| 📦npm | js-yaml | all versions | 3.14.2npm install js-yaml@3.14.2 |
Affected Products
js-yamlnodecaDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for js-yaml, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update js-yaml to 4.1.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mh29-5h37-fv8m 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.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.Source: Red Hat security advisory for GHSA-mh29-5h37-fv8m (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Ceph Storage 7.1 | rhceph/grafana-rhel9:1791450715 | RHSA-2026:83548 |
| Red Hat Ceph Storage 8.1 | rhceph/grafana-rhel9:1777566546 | RHSA-2026:15979 |
| Red Hat Ceph Storage 9.0 | rhceph/grafana-rhel10:1781018768 | RHSA-2026:26411 |
| Red Hat Openshift Data Foundation 4.18 | odf4/cephcsi-rhel9:1786705347 | RHSA-2026:56431 |
Frequently Asked Questions
Is GHSA-mh29-5h37-fv8m in your dependencies?
Find it across npm, including transitive dependencies.