GNU Bison Assertion Failure Vulnerability in obprintf.c via __obstack_vprintf_internal

An assertion failure vulnerability has been identified in GNU Bison versions prior to 3.8.2. This vulnerability occurs in the function __obstack_vprintf_internal within the file obprintf.c. The issue arises when Bison processes specially crafted grammar files that contain malformed '$variable' references. This manipulation leads to a reachable assertion, causing the program to terminate abruptly with a SIGABRT signal. The vulnerability is local, and an exploit is publicly available.

Impact

Exploitation of this vulnerability causes a denial-of-service condition by crashing the Bison process. The assertion failure indicates a buffer management issue in Bison's grammar processing, which can be triggered by various input files, demonstrating the vulnerability's widespread impact.

Reproduction

The vulnerability can be reproduced by using Bison to process a grammar file that includes malformed '$variable' references. This can be done by executing Bison with the file as an argument. The expected outcome is an assertion failure message indicating that the Bison process has crashed and generated a core dump.