Vulnerability in Mozilla Thunderbird

[ Why it matters ]Priority signals

• Critical severity: CVSS 9.8

[ Description ]Official description

Invalid pointer in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, and Firefox ESR 140.17.

[ 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
• CERT-FR30 Sep 2026CERTFR-2026-AVI-1240

  Multiple vulnerabilities in Mozilla products Translated from French

  Multiple vulnerabilities have been discovered in Mozilla products. 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/mfsa2026-100Vendor Advisory
• www.mozilla.org/security/advisories/mfsa2026-101Vendor Advisory
• www.mozilla.org/security/advisories/mfsa2026-102Vendor Advisory
• www.mozilla.org/security/advisories/mfsa2026-103Vendor Advisory
• www.mozilla.org/security/advisories/mfsa2026-97Vendor Advisory
• www.mozilla.org/security/advisories/mfsa2026-99Vendor Advisory