CVE-2026-110247
High
Description
Several buffer-growth sites in libmime performed size arithmetic in 32-bit types without overflow checks. On a sufficiently large message the growth guard could fail open, or the buffer could be reallocated smaller than required, and a subsequent memcpy would then write attacker-controlled data across adjacent heap allocations. This vulnerability was fixed in Thunderbird 158 and Thunderbird 153.6.
SeverityHigh
CVSS8.4
Exploit probability—
ProductLibmime
PublishedOct 13, 2026
First seenOct 13, 2026
Weakness typeCWE-190Integer overflow
How to fix
Update
- Thunderbird158, 153.6 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| libmime | No range specified | — |
| Thunderbird | No range specified | 158, 153.6 |
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