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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2026-58218?
How do I fix CVE-2026-58218?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-58218 being exploited?
There is no known exploitation of CVE-2026-58218 in the wild and no public exploit code.
Sources
Also known as AZL-94172, DEBIAN-CVE-2026-58218, ECHO-bb87-47c0-0473, GHSA-qcxx-8h4x-9v7w, UBUNTU-CVE-2026-58218.