What’s Vulnerable › Vulnerabilities

CVE-2026-110247: Integer overflow in libmime buffer growth could lead to heap corruption

• Severity: high (CVSS 8.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-13 · updated 2026-10-27
• Weakness: CWE-190

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.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=2071621
• https://www.mozilla.org/security/advisories/mfsa2026-109/
• https://www.mozilla.org/security/advisories/mfsa2026-122/

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