# 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.

- **Severity:** Medium 4.2 (`CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Sep 2026
- **Updated:** 11 Sep 2026
- **Also known as:** AZL-100019, BELL-CVE-2026-89092, DEBIAN-CVE-2026-89092, ECHO-44db-d5e5-4257, GHSA-gwqp-9qgw-c5pv, OESA-2026-4280, OESA-2026-4281, OESA-2026-4282, OESA-2026-4283, UBUNTU-CVE-2026-89092

## 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 (Memory Allocation with Excessive Size Value)

## Which versions are affected by CVE-2026-89092?


## How do I fix CVE-2026-89092?

Apply the vendor's patch.

## Is CVE-2026-89092 being exploited?

There is no known exploitation of CVE-2026-89092 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89092 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-89092 in the wild and no public exploit code.

Affected product: The GNU C Library glibc. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-89092/ (Markdown: https://insights.sbomify.com/CVE-2026-89092/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89092
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89092
- OSV: https://osv.dev/vulnerability/CVE-2026-89092

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-89092/
Summaries are generated and may contain mistakes; the official description above is the record.