Vulnerability in Mozilla Thunderbird

[ Description ]Official description

When authenticating to a POP3 or SMTP server using NTLM, Thunderbird did not check whether the server's challenge was valid base64. A malicious server could send a challenge that caused Thunderbird to include uninitialized heap memory in its NTLM response, disclosing that memory to the server. A challenge consisting only of base64 padding also caused an out-of-bounds read, crashing Thunderbird. This affected accounts configured to use NTLM or GSSAPI authentication. The uninitialized memory disclosure only affected NTLM. This vulnerability was fixed in Thunderbird 158.0.1 and Thunderbird 153.5.1.

[ Fixes ]Fixes and patches

• Security bulletin: Mozilla mfsa2026-115Vendor patch or bulletin · CERT-FR · mozilla.org/en-US/security/advisories/mfsa2026-115, cited by CERT-FR CERTFR-2026-AVI-1346
• Security bulletin: Mozilla mfsa2026-113Vendor patch or bulletin · CERT-FR · mozilla.org/en-US/security/advisories/mfsa2026-113, cited by CERT-FR CERTFR-2026-AVI-1346
• Security bulletin: Mozilla mfsa2026-114Vendor patch or bulletin · CERT-FR · mozilla.org/en-US/security/advisories/mfsa2026-114, cited by CERT-FR CERTFR-2026-AVI-1346
• Security bulletin: Mozilla mfsa2026-111Vendor patch or bulletin · CERT-FR · mozilla.org/en-US/security/advisories/mfsa2026-111, cited by CERT-FR CERTFR-2026-AVI-1346
• Security bulletin: Mozilla mfsa2026-112Vendor patch or bulletin · CERT-FR · mozilla.org/en-US/security/advisories/mfsa2026-112, cited by CERT-FR CERTFR-2026-AVI-1346

[ Advisories ]Government CERT advisories

• CERT-FR21 Oct 2026CERTFR-2026-AVI-1346

  Multiple vulnerabilities in Mozilla products Translated from French

  Multiple vulnerabilities have been discovered in Mozilla products. Some of them allow an attacker to cause arbitrary code execution, a breach of data confidentiality and denial of service.

  CVE-2026-113400CVE-2026-113470CVE-2026-113868+5 more CVEs
• BSI CERT-Bund20 Oct 2026WID-SEC-2026-4064

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

  Risk highCVE-2026-113866CVE-2026-113470CVE-2026-113399+5 more CVEs

[ References ]References

• bugzilla.mozilla.org/show_bug.cgi
• www.mozilla.org/security/advisories/mfsa2026-114
• www.mozilla.org/security/advisories/mfsa2026-115