CVE-2026-58218VulnerabilityPublished 28 Jul 2026Updated 6 Aug 2026

Samba's internal DNS server

Affects sambaSource GCVE Database

Authoritative record:CVE-2026-58218· Medium 5.3

Not known to be exploited · CVSS 5.3 Medium · fixed in 2:4.15.13+dfsg-0ubuntu1.13 : update samba when convenient.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.7% chance of exploitation in 30 days – higher than 55% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2:4.15.13+dfsg-0ubuntu1.13, 2:4.19.5+dfsg-4ubuntu9.7, 2:4.23.6+dfsg-1ubuntu2.2

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 30 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade the Ubuntu samba to 2:4.15.13+dfsg-0ubuntu1.13 (package) or 2:4.19.5+dfsg-4ubuntu9.7 (package) or 2:4.23.6+dfsg-1ubuntu2.2 (package).

Patches and advisories

ubuntu.com/security/notices/USN-8621-1 (opens in a new tab)

Affected software

Product	Affected	Fixed in
Ubuntu 26.04 LTSsamba`pkg:deb/ubuntu/samba?arch=source&distro=resolute`Other threats	Affected <2:4.23.6+dfsg-1ubuntu2.2	Fixed in 2:4.23.6+dfsg-1ubuntu2.2
Ubuntu 24.04 LTSsamba`pkg:deb/ubuntu/samba?arch=source&distro=noble`Other threats	Affected <2:4.19.5+dfsg-4ubuntu9.7	Fixed in 2:4.19.5+dfsg-4ubuntu9.7
Ubuntu 22.04 LTSsamba`pkg:deb/ubuntu/samba?arch=source&distro=jammy`Other threats	Affected <2:4.15.13+dfsg-0ubuntu1.13	Fixed in 2:4.15.13+dfsg-0ubuntu1.13
Ubuntu Pro 20.04 LTSsamba`pkg:deb/ubuntu/samba?arch=source&distro=esm-infra/focal`Other threats	Affected 2:4.10.7+dfsg-0ubuntu2 – 2:4.15.13+dfsg-0ubuntu0.20.04.8+esm2 37 affected builds	Fixed in–
Ubuntu Pro 18.04 LTSsamba`pkg:deb/ubuntu/samba?arch=source&distro=esm-infra/bionic`Other threats	Affected 2:4.6.7+dfsg-1ubuntu3 – 2:4.7.6+dfsg~ubuntu-0ubuntu2.29+esm3 32 affected builds	Fixed in–
Ubuntu Pro 16.04 LTSsamba`pkg:deb/ubuntu/samba?arch=source&distro=esm-infra/xenial`Other threats	Affected 2:4.1.17+dfsg-4ubuntu2 – 2:4.3.11+dfsg-0ubuntu0.16.04.34+esm4 46 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

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

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