CVE-2026-6791: the gnu c library glibc Stack-based Buffer Overflow

Vulnerability summary

CVE-2026-6791 is a medium (CVSS 6.6) Stack-based Buffer Overflow vulnerability in the gnu c library glibc. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 11.6% of scored vulnerabilities.

Timeline

1. 10-08-2026
   PublishedVulnerability first disclosed.
2. 12-08-2026
   Last modifiedVulnerability information updated.

Description

When expanding paths that begin with a tilde (~) followed by a username, the internal parse_tilde function extracts the username to determine the user's home directory. The implementation allocates memory for this username directly on the stack using the strndupa macro. Because the size of this allocation was determined by the length of the user-supplied input without any bounds checks, passing an excessively long username e.g. thousands of characters, forces the thread to exhaust its stack space. Thus if an application passes untrusted, attacker-controlled input to the wordexp function, an attacker can trigger a stack clash.

• CWE-121Stack-based Buffer OverflowA stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).