CVE-2026-6791 Affecting glibc package, versions <2.43-r10

Note: Versions mentioned in the description apply only to the upstream glibc package and not the glibc package as distributed by Chainguard. See How to fix? for Chainguard relevant fixed versions and status.

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.

• https://sourceware.org/bugzilla/show_bug.cgi?id=34091