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glibc can exhaust stack with long username input
published 2 months ago
Summary
The glibc library used in Azure can run out of stack space if it receives an extremely long user name when expanding file paths. This may cause the affected program to stop working, leading to a denial of service. Update glibc to the latest patched version or avoid passing untrusted user‑provided strings to the wordexp function.
What to do
The CVE record does not list a fixed version. Check the vendor's site or the advisory links below - a fix may already be released.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| Azure Linux:3 | azure | glibc | <= 2.38-21 |
Original advisory text
CVE-2026-6791 affecting package glibc 2.38-21
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.
References
Timeline
Published10 Aug 2026
Updated23 Sep 2026
First seen23 Sep 2026
Sources
AZL-95492 · OSV
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