Vulnerability in Mozilla Thunderbird

[ Description ]Official description

An attacker could cause a heap buffer overflow by getting a user to open an email that is greater than or equal to 2GB in size. This vulnerability was fixed in Thunderbird 157, Thunderbird 140.17, and Thunderbird 153.4.

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ Advisories ]Government CERT advisories

• CERT-FR1 Oct 2026CERTFR-2026-AVI-1244

  Multiple vulnerabilities in Mozilla Thunderbird Translated from French

  Multiple vulnerabilities have been discovered in Mozilla Thunderbird. Some of them allow an attacker to cause privilege escalation, remote denial of service and a breach of data confidentiality.

  CVE-2026-100786CVE-2026-100763CVE-2026-100796+75 more CVEs
• BSI CERT-Bund29 Sep 2026WID-SEC-2026-3654

  Mozilla Firefox, Firefox ESR and Thunderbird: Multiple vulnerabilities Translated from German

  CVE-2026-100798CVE-2026-100831CVE-2026-100764+75 more CVEs

[ References ]References

• bugzilla.mozilla.org/show_bug.cgiPermissions Required
• www.mozilla.org/security/advisories/mfsa2026-101Vendor Advisory
• www.mozilla.org/security/advisories/mfsa2026-102Vendor Advisory
• www.mozilla.org/security/advisories/mfsa2026-103Vendor Advisory