CVE-2026-3889: Mozilla Thunderbird · CWE-451
Affects Mozilla ThunderbirdSource CVE Database V5
Not known to be exploited · CVSS 6.5 Medium · patch available : update Mozilla Thunderbird when convenient.
Data as of 30 Oct 2026, 11:52 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 10% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:NExploitation evidence
Disclosed: evidence found.
CVE published 24 Mar 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 30 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Mozilla Thunderbird | Affected
| Fixed in
|
AI-suggested
Mozilla has released official fixes for this vulnerability in Thunderbird versions 149 and 140.9. Users should update to these versions to remediate the issue. The vendor advisory notes that no additional action is required beyond applying these updates. Since Thunderbird is not a cloud service, remediation depends on user-side patching. Patch status is confirmed by the Mozilla Foundation Security Advisories MFSA2026-23 and MFSA2026-24.
Description
Spoofing issue in Thunderbird. This vulnerability was fixed in Thunderbird 149 and Thunderbird 140.9.