CVE-2025-64718 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.
js-yaml has prototype pollution in merge (<<)
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 CVE-2025-64718.
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.
How urgent is this, really
CVE-2025-64718 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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 |
Detection & 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 CVE-2025-64718 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-64718 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-64718. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
| Product | Fixed in | Advisory |
|---|---|---|
| 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 CVE-2025-64718 in your dependencies?
O3 Security finds CVE-2025-64718 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.