# CVE-2026-6238: Buffer overread in ns_printrrf with corrupted RDATA field

> An attacker can cause a crash or read uninitialized memory in applications using deprecated glibc DNS debugging functions via a crafted DNS response.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Apr 2026
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-85004, BELL-CVE-2026-6238, CLSA-2026-1780916496, DEBIAN-CVE-2026-6238, ECHO-916f-8705-1b52, GHSA-h8wx-jcwq-g3cp, MINI-9482-2jh4-39pv, MINI-9p64-m6c8-jxc2, MINI-f764-5hrx-hg8v, ROOT-OS-DEBIAN-11-CVE-2026-6238, ROOT-OS-DEBIAN-12-CVE-2026-6238, ROOT-OS-DEBIAN-13-CVE-2026-6238, UBUNTU-CVE-2026-6238

## What is CVE-2026-6238?

CVE-2026-6238 is a medium-severity memory corruption vulnerability in Gnu Glibc, published on 28 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The deprecated functions ns_printrrf, ns_printrr and fp_nquery in the GNU C Library version 2.0.1 to version 2.43 fail to validate the RDATA content against the RDATA length in a DNS response when processing A6, CERT, LOC, TKEY or TSIG records, which may allow an attacker to craft a DNS response, causing a target application to crash or read uninitialized memory.

These functions are for application debugging only and hence not in the path of code executed by the DNS resolver.  Further, they have been deprecated since version 2.34 and should not be used by any new applications.  Applications should consider porting away from these interfaces since they may be removed in future versions.

Weakness: CWE-126 (Buffer Over-read)

## Which versions are affected by CVE-2026-6238?

It affects 1 product.


Products: Gnu Glibc.

## How do I fix CVE-2026-6238?

Upgrade to a fixed version.

## Is CVE-2026-6238 being exploited?

There is no known exploitation of CVE-2026-6238 in the wild and no public exploit code.

## Other vulnerabilities in Gnu Glibc

- [CVE-2026-5450](https://insights.sbomify.com/CVE-2026-5450/): scanf %mc off-by-one heap buffer overflow (critical 9.8)
- [CVE-2023-25139](https://insights.sbomify.com/CVE-2023-25139/): Memory corruption in n/a (critical 9.8)
- [CVE-1999-0199](https://insights.sbomify.com/CVE-1999-0199/): Other in n/a (critical 9.8)
- [CVE-2019-1010022](https://insights.sbomify.com/CVE-2019-1010022/): Security feature bypass in glibc (critical 9.8)
- [CVE-2005-3590](https://insights.sbomify.com/CVE-2005-3590/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-6238 and fix it if it is affected.

What it is: CVE-2026-6238 is a medium-severity memory corruption vulnerability in Gnu Glibc, published on 28 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-6238 in the wild and no public exploit code.

Affected product: Gnu 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-2026-6238/ (Markdown: https://insights.sbomify.com/CVE-2026-6238/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-6238
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-6238
- OSV: https://osv.dev/vulnerability/CVE-2026-6238

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-6238/
Summaries are generated and may contain mistakes; the official description above is the record.