CVE-2026-59869
HIGHjs-yaml: YAML merge-key chains can force quadratic CPU consumption
Description
js-yaml is a JavaScript YAML parser and dumper. From 3.0.0 before 3.15.0 and from 4.0.0 before 4.3.0, js-yaml can spend quadratic CPU time parsing a document whose size grows only linearly when a chain of mappings uses merge keys where each mapping merges the previous one. This issue is fixed in versions 3.15.0 and 4.3.0.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. 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.
Remediation status
No patched version of the affected component has shipped for CVE-2026-59869 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
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 CVE-2026-59869 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-2026-59869. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-59869 in your dependencies?
O3 detects CVE-2026-59869 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.