Multiple vulnerabilities in Firefox and Thunderbird
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Multiple vulnerabilities in Mozilla Firefox and Thunderbird allow privilege escalation, denial of service, and data confidentiality breaches.
CERT-FR has published a security advisory covering multiple vulnerabilities affecting Mozilla Firefox and Thunderbird across multiple release channels. Affected versions include Firefox ESR versions prior to 115.41, 140.16, and 153.3; Firefox versions prior to 156; Thunderbird ESR versions prior to 140.16; and Thunderbird versions prior to 156. The vulnerabilities enable attackers to achieve privilege escalation, remote denial of service, bypass security policies, and compromise data confidentiality. The advisory references six Mozilla security bulletins (MFSA2026-90 through MFSA2026-95) published on September 15, 2026, which contain the detailed technical descriptions and patch information. Defenders should consult the Mozilla security advisories for specific CVE details and apply the corresponding patches to all affected Firefox and Thunderbird installations.
Mentioned in this report
Source reporting: https://www.cert.ssi.gouv.fr/avis/CERTFR-2026-AVI-1183
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