CVE-2026-110247: libmime performed size arithmetic · Several Buffer-growth Sites
Source GCVE Database
Not known to be exploited · CVSS 8.4 High.
Data as of 27 Oct 2026, 22:13 UTC
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 13 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 Oct 2026.
What to do
AI-suggested
This vulnerability is fixed in Thunderbird 158. Users and administrators should upgrade to Thunderbird 158 or later to remediate this issue. No additional mitigation steps are required as the fix fully addresses the vulnerability.
Description
CVE-2026-110247 is a high-severity vulnerability in Thunderbird's libmime library where size arithmetic was performed using 32-bit types without proper overflow checks. This flaw could cause heap corruption by allowing a buffer to be reallocated smaller than required, leading to attacker-controlled data overwriting adjacent heap allocations. The issue was fixed in Thunderbird version 158.