Vulnerability in Mozilla Thunderbird

[ Description ]Official description

Thunderbird did not escape attribute values when serializing outgoing XMPP stanzas. Because values from incoming requests were echoed back in automatic replies, a remote XMPP user could send a crafted request that caused Thunderbird to inject arbitrary stanzas into the user's connection, which the server would then process as if sent by the user. This could be used to send messages or change contact and subscription settings on behalf of the user, without any interaction. This bug only affects Thunderbird's chat feature with XMPP accounts. 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