# CVE-2026-93009: Dnsmasq: dnsmasq: heap out-of-bounds read in dhcpv6 option 39 fqdn decoder


- **Severity:** Medium 4.3 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 29 Oct 2026
- **Updated:** 29 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-93009, GHSA-6qrc-rpqw-59wp

## What is CVE-2026-93009?

CVE-2026-93009 is a medium-severity vulnerability in Red Hat Ceph Storage 9, published on 29 Oct 2026. 

### Official description

A flaw was found in dnsmasq. The DHCPv6 client hostname parser can read one byte past the end of a crafted FQDN option because it checks the next label length before confirming the pointer is still inside the option. An attacker on the local network can trigger this with a single DHCPv6 packet. The extra byte is not returned to the client or logged, and no crash has been demonstrated.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-93009?


## How do I fix CVE-2026-93009?

No fix has been published for CVE-2026-93009 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-93009 being exploited?

There is no known exploitation of CVE-2026-93009 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93009 and fix it if it is affected.

What it is: CVE-2026-93009 is a medium-severity vulnerability in Red Hat Ceph Storage 9, published on 29 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-93009 in the wild and no public exploit code.

Affected product: Red Hat Ceph Storage 9. 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-2026-93009/ (Markdown: https://insights.sbomify.com/CVE-2026-93009/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93009
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93009
- OSV: https://osv.dev/vulnerability/CVE-2026-93009

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93009/
Summaries are generated and may contain mistakes; the official description above is the record.