A flaw has been found in GNU Bison up to 3.8.2. This affects the function __obstack_vprintf_internal of the file obprintf.c. Executing manipulation can lead to reachable assertion. The attack requires local access. The exploit has been published and may be used. It is still unclear if this vulnerability genuinely exists. The issue could not be reproduced from a GNU Bison 3.8.2 tarball run in a Fedora 42 container.
The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.
While assertion is good for catching logic errors and reducing the chances of reaching more serious vulnerability conditions, it can still lead to a denial of service. For example, if a server handles multiple simultaneous connections, and an assert() occurs in one single connection that causes all other connections to be dropped, this is a reachable assertion that leads to a denial of service.