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CVE-2026-50252VulnerabilityPublished Updated

In NLnet Labs Unbound 1.4.22 up to and including 1.25.1, UDP source port is randomized and intended to serve as a

Affects unboundSource GCVE Database

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Authoritative record:CVE-2026-50252· Medium 5.7

Public exploit available · CVSS 5.7 Medium · fixed in 1.4.22-1ubuntu4.14.04.3+esm5 : patch unbound as a priority.

Data as of 11 Nov 2026, 12:39 UTC

CVSS 4.0 base score
5.7Medium
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 1.4.22-1ubuntu4.14.04.3+esm5, 1.5.8-1ubuntu1.1+esm5, 1.6.7-1ubuntu2.6+esm6 +5
CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:H/E:P/U:Amber

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 22 Jul 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: evidence found.

    CVSS exploit maturity: proof of concept public

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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), CVSS vector, the Metasploit, Exploit-DB and nuclei-templates index as of 11 Nov 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
Ubuntu 26.10unboundpkg:deb/ubuntu/unbound?arch=source&distro=stonkingOther threatsAffected
  • <1.25.1-1ubuntu3.1
Fixed in
  • 1.25.1-1ubuntu3.1
Ubuntu 26.04 LTSunboundpkg:deb/ubuntu/unbound?arch=source&distro=resoluteOther threatsAffected
  • <1.24.2-1ubuntu2.4
Fixed in
  • 1.24.2-1ubuntu2.4
Ubuntu 24.04 LTSunboundpkg:deb/ubuntu/unbound?arch=source&distro=nobleOther threatsAffected
  • <1.19.2-1ubuntu3.12
Fixed in
  • 1.19.2-1ubuntu3.12
Ubuntu 22.04 LTSunboundpkg:deb/ubuntu/unbound?arch=source&distro=jammyOther threatsAffected
  • <1.13.1-1ubuntu5.17
Fixed in
  • 1.13.1-1ubuntu5.17
Ubuntu Pro 20.04 LTSunboundpkg:deb/ubuntu/unbound?arch=source&distro=esm-infra/focalOther threatsAffected
  • <1.9.4-2ubuntu1.11+esm3
Fixed in
  • 1.9.4-2ubuntu1.11+esm3
Ubuntu Pro 18.04 LTSunboundpkg:deb/ubuntu/unbound?arch=source&distro=esm-infra/bionicOther threatsAffected
  • <1.6.7-1ubuntu2.6+esm6
Fixed in
  • 1.6.7-1ubuntu2.6+esm6

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

AI-suggested

A patch is available and should be applied to affected Unbound versions. Fixed versions include 1.4.22-1ubuntu4.14.04.3+esm5, 1.5.8-1ubuntu1.1+esm5, 1.6.7-1ubuntu2.6+esm6, 1.9.4-2ubuntu1.11+esm3, 1.13.1-1ubuntu5.17, 1.19.2-1ubuntu3.12, 1.24.2-1ubuntu2.4, and 1.25.1-1ubuntu3.1. Users should upgrade to these versions as soon as possible. Refer to the official Ubuntu security notices USN-8946-1 and USN-8946-2 for detailed patch information.

Description

NLnet Labs Unbound versions from 1.4.22 up to and including 1.25.1 have a vulnerability related to UDP source port randomization used for DNS transaction entropy. When the SO_REUSEPORT option is enabled (which is the default), the UDP source port space is partitioned among worker threads, allowing an attacker to infer which thread handled a query based on the source port. This reduces the effective randomness and enables DNS cache poisoning attacks by lowering the random port population per thread.

References

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