CVE-2026-110247

A flaw was found in Thunderbird. A remote attacker could exploit an integer overflow in the libmime library to achieve arbitrary code execution or cause a Denial of Service (DoS). By sending a sufficiently large email message, an attacker causes buffer size arithmetic to overflow without proper checks. This leads to heap memory corruption as subsequent memory copy operations overwrite adjacent heap allocations with attacker-controlled data.

Red Hat evaluates this vulnerability with an Important severity rating because it presents a risk of remote arbitrary code execution and application crashes within the context of the desktop user. Although the issue can be reached remotely by delivering a specially crafted email message, exploitation requires user interaction to process the message and does not directly compromise the underlying host or grant elevated privileges. Because Thunderbird operates as an interactive end-user client rather than an exposed system service, the immediate impact is bounded to the affected user's session.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.