CVE-2026-103500

A flaw was found in Thunderbird. A remote attacker could exploit this vulnerability by convincing a user to open an email that is 2GB or larger, triggering a heap buffer overflow. This flaw allows an attacker to corrupt memory, which may cause an application crash, resulting in a Denial of Service (DoS), or potentially lead to arbitrary code execution.

An important impact heap buffer overflow vulnerability was found in Thunderbird as shipped in Red Hat Enterprise Linux 8, 9, and 10, Red Hat In-Vehicle OS, and Fedora. A remote attacker could exploit this flaw by convincing a user to open an email message that is 2GB or larger in size, triggering a heap buffer overflow that corrupts memory. This can cause the application to crash, resulting in a denial of service, or potentially lead to arbitrary code execution. Fixes are being pursued for the affected Red Hat product streams, which are handled through delegated Thunderbird package updates. Red Hat rates this flaw Important severity (CVSS 8.8), which differs from the Moderate rating assigned by NIST (CVSS 6.1); Red Hat's rating reflects the potential for memory corruption and arbitrary code execution via a remotely delivered crafted email.

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.