Use-After-Free in Firefox (CVE-2026-109729)
Summary
Vulnerability in Firefox (CVE-2026-109729). Risk of unauthorized operations or information disclosure.
Original description
The description as published by the source.
Use-after-free in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 158, Firefox ESR 115.43, and Firefox ESR 153.5.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-109729 has been found in Firefox.
Risk of unauthorized operations or information disclosure. CVSS score: 5.4/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Firefox CVE-2026-109729" on the vendor's site.
CVE-2026-109729 (Firefox) — CWE-416 / CVSS v3 5.4
Attack vector: remote (network-reachable) / unauthenticated
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Use-after-free (CWE-416) exists in Firefox.
Check the vendor advisory for the affected versions of Firefox.
Severity: Medium (CVSS 5.4/10). Risk of unauthorized operations or information disclosure.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Firefox' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'Firefox' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
Firefoxを grep し、稼働しているサービス・バージョンを把握する。 -
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
References
- REDHAT Red Hat
- web bugzilla.mozilla.org
- web security@mozilla.org
- web security@mozilla.org
- web security@mozilla.org
- web nvd.nist.gov
- web mozilla.org
- web mozilla.org
- web mozilla.org
- web github.com
- web security@mozilla.org
- web security@mozilla.org
- web mozilla.org
- web mozilla.org