Buffer Overflow Vulnerability in Thunderbird by Mozilla

CVE-2026-110247

What is CVE-2026-110247?

A significant buffer overflow vulnerability exists in the libmime library of Thunderbird, where size calculations can lead to inadequate overflow checks. This flaw may cause a failure in the growth guard mechanism or result in the reallocation of buffers that are smaller than necessary. Consequently, this can allow an attacker to overwrite adjacent heap data with controlled inputs during memory operations. Users are advised to upgrade to Thunderbird 158 or later to mitigate this security risk.

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