# CVE-2026-58218: Samba: dns signing dos via tkey name cache exhaustion

> Remote attackers can exhaust the TKEY name cache in Samba's DNS server, causing denial of service by blocking legitimate TSIG authentication.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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:** 30 Jul 2026
- **Updated:** 30 Jul 2026
- **Also known as:** AZL-94172, DEBIAN-CVE-2026-58218, ECHO-bb87-47c0-0473, GHSA-qcxx-8h4x-9v7w, UBUNTU-CVE-2026-58218

## What is CVE-2026-58218?

CVE-2026-58218 is a medium-severity denial of service vulnerability in Red Hat Enterprise Linux 10, published on 30 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw was found in Samba's internal DNS server where unauthenticated TKEY registration requests were added to the TKEY name cache before being rejected. A remote, unauthenticated attacker can exploit this behavior by sending a large number of TKEY requests with arbitrary names, exhausting the cache and evicting legitimate TKEY entries. This can prevent legitimate TSIG authentication for signed DNS queries, resulting in a denial of service.

Weakness: CWE-410 (Insufficient Resource Pool)

## Which versions are affected by CVE-2026-58218?


## How do I fix CVE-2026-58218?

Apply the vendor's patch.

## Is CVE-2026-58218 being exploited?

There is no known exploitation of CVE-2026-58218 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-58218 and fix it if it is affected.

What it is: CVE-2026-58218 is a medium-severity denial of service vulnerability in Red Hat Enterprise Linux 10, published on 30 Jul 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-2026-58218 in the wild and no public exploit code.

Affected product: Red Hat Enterprise Linux 10. 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-2026-58218/ (Markdown: https://insights.sbomify.com/CVE-2026-58218/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-58218
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-58218
- OSV: https://osv.dev/vulnerability/CVE-2026-58218

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-58218/
Summaries are generated and may contain mistakes; the official description above is the record.