CVE-2026-89092 Stack overflow in nscd due to unbounded alloca use
A malicious DNS server can cause a stack overflow in nscd, leading to service crashes and degraded DNS resolution on systems using untrusted DNS.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89092?
CVE-2026-89092 is a medium-severity denial of service vulnerability in The GNU C Library glibc, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
The nscd service in the GNU C Library 2.3.4 onwards may crash due to a stack overflow when a malicious DNS server returns too large a response for a DNS query, resulting in degraded DNS resolution for the system.
Exploitation of this bug needs a system that has nscd enabled and using an untrusted DNS server for name resolution, with the compromised DNS server being capable of processing records large enough to result in a stack overflow in an nscd thread stack. During experimentation, bind 9 was unable to handle large records, but that could change in future or with a different name server. In typical installations, nscd is executed in an isolated context as its own user without a shell, due to which any compromise of that service is isolated.
There is a remote possibility of nscd cache corruption if an attacker manages to get the stack pointer into a desired point in the heap, potentially resulting in other caches in nscd being overwritten with corrupt data through the stack overflow, until the buggy code path eventually results in a crash.
Finally, a crash in nscd may result in performance degradation when resolving names, but it does not result in a denial of service.
Weakness: CWE-789
Which versions are affected by CVE-2026-89092?
How do I fix CVE-2026-89092?
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-2026-89092 being exploited?
There is no known exploitation of CVE-2026-89092 in the wild and no public exploit code.
Sources
Also known as AZL-100019, BELL-CVE-2026-89092, DEBIAN-CVE-2026-89092, ECHO-44db-d5e5-4257, GHSA-gwqp-9qgw-c5pv, OESA-2026-4280 and 4 more.