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VulnerabilityPublished Updated

CVE-2026-92240: Mozilla Thunderbird · Out-of-bounds Read

Affects Mozilla ThunderbirdSource CVE Database V5

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Not known to be exploited · CVSS 9.1 Critical · fixed in 140.16 : patch Mozilla Thunderbird as a priority.

Data as of 30 Oct 2026, 20:25 UTC

CVSS 3.1 base score
9.1Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.6% chance of exploitation in 30 days – higher than 50% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 140.16
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 15 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 30 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
Mozilla ThunderbirdAffected
  • <140.16
Fixed in
  • 140.16

AI-suggested

This vulnerability is fixed in Thunderbird versions 140.16 and 156. Users should update to at least Thunderbird 140.16 or later to remediate this issue. No additional mitigation actions are required as the fix is officially released by Mozilla.

Description

A malicious or compromised IMAP server can trigger an out-of-bounds read in the IMAP response parser by sending an untagged '* ID' response, crashing Thunderbird. The affected parsing path is reachable before authentication. This vulnerability was fixed in Thunderbird 156, Thunderbird 140.16, and Thunderbird 153.3.

References

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