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
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
- 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:AmberExploitation evidence
Disclosed: evidence found.
CVE published 22 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
CVSS exploit maturity: proof of concept public
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), 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.
Patches and advisories
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.10unboundpkg:deb/ubuntu/unbound?arch=source&distro=stonkingOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSunboundpkg:deb/ubuntu/unbound?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSunboundpkg:deb/ubuntu/unbound?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 22.04 LTSunboundpkg:deb/ubuntu/unbound?arch=source&distro=jammyOther threats | Affected
| Fixed in
|
Ubuntu Pro 20.04 LTSunboundpkg:deb/ubuntu/unbound?arch=source&distro=esm-infra/focalOther threats | Affected
| Fixed in
|
Ubuntu Pro 18.04 LTSunboundpkg:deb/ubuntu/unbound?arch=source&distro=esm-infra/bionicOther threats | Affected
| Fixed in
|
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
- ubuntu.com/security/CVE-2026-50252 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-50252 (opens in a new tab)
- community.nlnetlabs.nl/t/unbound-1-25-2-released/3430 (opens in a new tab)
- ubuntu.com/security/notices/USN-8946-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8946-2 (opens in a new tab)