CVE-2026-110247 Integer overflow in libmime buffer growth could lead to heap corruption
An integer overflow in libmime buffer growth allows heap corruption and potential code execution via crafted messages in Thunderbird.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-110247?
CVE-2026-110247 is a high-severity vulnerability in Mozilla Thunderbird, published on 13 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Weakness: CWE-190
Which versions are affected by CVE-2026-110247?
How do I fix CVE-2026-110247?
No fix has been published for CVE-2026-110247 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-110247 being exploited?
There is no known exploitation of CVE-2026-110247 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-110247, GHSA-6c5g-4xv7-7fmm, UBUNTU-CVE-2026-110247.