CVE-2026-100788: Mozilla Thunderbird · CWE-824
Affects Mozilla ThunderbirdSource CVE Database V5
Not known to be exploited · CVSS 9.8 Critical.
Data as of 12 Nov 2026, 23:24 UTC
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 36% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 29 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.
What to do
AI-suggested
This vulnerability has been fixed by Mozilla in Thunderbird versions 157, 140.17, and 153.4, as well as in Firefox ESR 153.4, Firefox 157, and Firefox ESR 140.17. Users and administrators should update to these fixed versions or later to mitigate the risk. No additional mitigation steps are indicated by the vendor advisory.
Description
CVE-2026-100788 is a critical vulnerability in Mozilla Thunderbird involving an invalid pointer in the JavaScript WebAssembly component. This flaw allows for potential high impact on confidentiality, integrity, and availability. The issue has been fixed in multiple versions of Thunderbird and Firefox, including Thunderbird 157, 140.17, and 153.4. The vulnerability is tracked under CWE-824 and has a CVSS score of 9.8, indicating critical severity.
References
- bugzilla.mozilla.org/show_bug.cgi?id=2072413 (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-100/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-97/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-99/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-101/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-102/ (opens in a new tab)
- mozilla.org/security/advisories/mfsa2026-103/ (opens in a new tab)