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Fencer Vulns
medium 5.3

CVE-2026-58218 json

Samba: dns signing dos via tkey name cache exhaustion

published 2026-07-30 3 mo ago modified 2026-07-30 3 mo ago also EUVD-2026-51128

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.8%
EPSS 0.8% chance of exploitation in 30 days, percentile 56%
public exploits
0
none known

Summary

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.

Patch / fix

  • samba Debian 13 2:4.22.10+dfsg-0+deb13u2
  • samba Debian 14 2:4.24.5+dfsg-1

debian advisories DEBIAN-CVE-2026-58218

  • samba Ubuntu 22.04 LTS 2:4.15.13+dfsg-0ubuntu1.13
  • samba Ubuntu 24.04 LTS 2:4.19.5+dfsg-4ubuntu9.7
  • samba Ubuntu 26.04 LTS 2:4.23.6+dfsg-1ubuntu2.2

ubuntu advisories UBUNTU-CVE-2026-58218

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • samba SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 4.22.11+git.552.66cfeb7de0a-160000.1.1
  • samba Linux Micro 6.2 4.22.9+git.538.af6cb4fb2e-160000.1.1
  • samba SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS, SLE High Availability Extension 12 SP5 4.15.13+git.729.a8ce057e8d-3.109.1
  • samba Enterprise Storage 7.1 4.15.13+git.808.eeca19f5e1-150300.3.106.1
  • samba SLES for SAP 15 SP5, SLES 15 SP5-LTSS, SLE Micro 5.5 +3 more 4.17.12+git.581.f49579c6cd-150500.3.42.1
  • samba SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE High Availability Extension 15 SP6 4.19.8+git.501.67274891bc-150600.3.29.1
  • samba SLE Module for Basesystem 15 SP7, SLE High Availability Extension 15 SP7 4.21.10+git.533.31d7e5508d-150700.3.29.1
  • samba SLES for SAP 15 SP4, SLES 15 SP4-LTSS, SLE Micro 5.4 +4 more 4.15.13+git.808.eeca19f5e1-150400.3.52.1

suse advisories SUSE-SU-2026:23003-1SUSE-SU-2026:23129-1SUSE-SU-2026:23152-1SUSE-SU-2026:22977-1SUSE-SU-2026:3367-1SUSE-SU-2026:3366-1

  • samba openSUSE Leap 16.0 4.22.11+git.552.66cfeb7de0a-160000.1.1
  • samba openSUSE Tumbleweed 4.24.5+git.481.dba78dbdea-1.1
  • samba openSUSE Leap 16.0 4.22.9+git.538.af6cb4fb2e-160000.1.1

opensuse advisories openSUSE-SU-2026:21540-1openSUSE-SU-2026:11431-1openSUSE-SU-2026:21475-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-58218 updated cvss 5.3

samba: DNS signing DoS via TKEY name cache exhaustion

  • Red Hat Enterprise Linux 6 samba, samba4, samba4-dc, samba-swat, samba4-libs, samba4-pidl, +17 more Red Hat Enterprise Linux 7 ctdb, samba, samba-dc, ctdb-tests, samba-libs, samba-pidl, +18 more Red Hat Enterprise Linux 8 ctdb, samba, libnetapi, ctdb-tests, samba-libs, samba-pidl, +24 more Red Hat Enterprise Linux 9 ctdb, samba, libldb, ldb-tools, libnetapi, samba-libs, +27 more Red Hat Enterprise Linux 10 samba Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9
    +1 more products
    Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.78% chance of exploitation in the next 30 days, higher than 56% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected products

  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 6
  • Red Hat Red Hat Enterprise Linux 7
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat OpenShift Container Platform 4

Classification

Weakness
  • CWE-410 Insufficient Resource Pool

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.