# CVE-2026-89092: GNU C Library nscd stack overflow in DNS cache handling

Source: https://junglewise.ai/threats/cve-2026-89092-gnu-c-library-nscd-stack-overflow-in-dns-cache-handling  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-11. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-89092 · Severity: medium · CVSS 4.2 · Published 2026-09-11

The nscd service, which handles DNS name resolution caching on Linux systems, can crash when a malicious DNS server returns an unusually large response. This causes temporary slowdowns in DNS lookups across the system. While the risk is limited to systems using untrusted DNS servers and the service runs in isolation, a sophisticated attacker could potentially corrupt the DNS cache before causing a crash.

Technologies: [Gnu C Library](https://junglewise.ai/threats/technologies/c-library). Vendors: [Gnu](https://junglewise.ai/threats/vendors/gnu).

## Quick answers

**Is CVE-2026-89092 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-89092 being exploited in the wild.

**How severe is CVE-2026-89092?** Medium severity, with a CVSS score of 4.2, published 11 September 2026.

**Which products and versions are affected?** Gnu C Library 2.3.4 and later.

**Is there a fix for CVE-2026-89092?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-89092 attacked?** It is attacked over the network or from the adjacent network, in a software library.

**Am I affected by CVE-2026-89092?** Check whether you run Gnu C Library at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a stack overflow in the nscd service (in glibc 2.3.4 and later) caused by unbounded alloca() calls in aicache.c and hstcache.c. When a DNS server returns a response larger than expected, the dynamic memory allocation via alloca() can overflow the thread's stack. The attack requires nscd to be enabled, the system to use an untrusted DNS server, and the DNS server to be capable of generating sufficiently large responses; this is difficult to trigger in practice with standard DNS servers like BIND 9. Successful exploitation results in a crash of the nscd daemon, degrading DNS resolution performance. There is a theoretical possibility of cache corruption if an attacker can manipulate the stack pointer to target the heap, potentially overwriting other nscd caches before the crash occurs.

## Affected products

- GNU C Library 2.3.4 and later

## Timeline

- 2026-09-10: disclosed
- 2026-09-11: advisory

## References

- [https://sourceware.org/bugzilla/show_bug.cgi?id=34624](https://sourceware.org/bugzilla/show_bug.cgi?id=34624)
- [https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0016](https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0016)

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