# CVE-2026-124858

Use-after-free in Firefox/Thunderbird HTML parser enabling potential remote code execution

- Page: https://www.vulneraibility.com/cve/CVE-2026-124858
- CVSS: 8.8
- Known exploited: not in CISA KEV as of our last sync
- EPSS: 0.40% (percentile 34.4)
- CISA SSVC: exploitation none, automatable no, technical impact total (assessed 2026-11-10)
- Weakness: CWE-416
- Published: 2026-11-10

## Affected

- Mozilla Firefox < 160
- Firefox ESR < 115.45
- Firefox ESR < 153.7
- Thunderbird < 160
- Thunderbird < 153.7

## Impact

Potential remote code execution via crafted web content rendering (use-after-free), allowing browser compromise or arbitrary code execution.

## Action

Immediate action required

## Recommendation

Update to fixed Firefox/Thunderbird versions immediately; block or avoid untrusted sites until patched.

## References

- [other] https://bugzilla.mozilla.org/show_bug.cgi?id=2074172
- [other] https://www.mozilla.org/security/advisories/mfsa2026-125/
- [other] https://www.mozilla.org/security/advisories/mfsa2026-126/
- [other] https://www.mozilla.org/security/advisories/mfsa2026-127/
- [other] https://www.mozilla.org/security/advisories/mfsa2026-128/
- [other] https://www.mozilla.org/security/advisories/mfsa2026-129/

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Summary, impact and action are written by the vulneraibility.com AI analysis pipeline from the CVE record, NVD, CISA and FIRST data; verify against the references.