CVE-2026-6791 Potential stack-based buffer clash during tilde expansion in wordexp
An attacker can cause a denial of service via stack exhaustion in glibc's wordexp function by providing an excessively long username during tilde expansion.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-6791?
CVE-2026-6791 is a medium-severity denial of service vulnerability in The GNU C Library glibc, published on 10 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-121
Which versions are affected by CVE-2026-6791?
How do I fix CVE-2026-6791?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-6791 being exploited?
There is no known exploitation of CVE-2026-6791 in the wild and no public exploit code.
Sources
Also known as AZL-95492, BELL-CVE-2026-6791, DEBIAN-CVE-2026-6791, ECHO-9658-3093-2999, GHSA-ch73-g8qv-r6r5, MINI-4xxf-44hj-m8hg and 1 more.