CERT-FR Flags Multiple Mozilla Product Flaws
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CERT-FR advisory covers multiple Firefox and Thunderbird vulnerabilities allowing code execution, data disclosure, or denial of service; patches available.
CERT-FR has issued an advisory consolidating multiple Mozilla security bulletins (MFSA2026-111 through MFSA2026-115) published on 20 October 2026, covering vulnerabilities across Firefox, Firefox ESR, and Thunderbird. The flaws collectively allow an attacker to achieve arbitrary code execution, compromise data confidentiality, or cause denial of service, with some issues unspecified in impact by the vendor. Affected versions include Firefox ESR prior to 115.43.1 and 153.5.1, Firefox prior to 158.0.1, and Thunderbird prior to 153.5.1 and 158.0.1.
Eight CVEs are referenced (CVE-2026-113399, -113400, -113401, -113470, -113866, -113867, -113868, -113869). No exploitation in the wild is mentioned in this advisory. Defenders should update affected Firefox and Thunderbird installations to the fixed versions referenced in the Mozilla security bulletins as soon as possible, prioritizing systems where arbitrary code execution could have the highest impact.
Mentioned in this report
Source reporting: https://www.cert.cyber.gouv.fr/avis/CERTFR-2026-AVI-1346
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