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

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-30 · updated 2026-07-30
Weakness: CWE-410

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.

References

https://access.redhat.com/security/cve/CVE-2026-58218
https://bugzilla.redhat.com/show_bug.cgi?id=2502728
https://bugzilla.samba.org/show_bug.cgi?id=16115
https://www.samba.org/samba/security/CVE-2026-58218.html

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