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VulnerabilityPublished Updated

CVE-2026-100788: Mozilla Thunderbird · CWE-824

Affects Mozilla ThunderbirdSource CVE Database V5

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Not known to be exploited · CVSS 9.8 Critical.

Data as of 12 Nov 2026, 23:24 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
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:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 29 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

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