🛡️ CVE-2026-42955 — unbound

🟢 CVSS 3.7 — Low ✅ No Known Exploit CWE-672 NVD
3.7
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

In NLnet Labs Unbound 1.16.2 up to and including 1.25.1, a similar vulnerability as with CVE-2026-40622 in the 'ghost domain names' family of attacks was found in Unbound that could extend the ghost domain window by up to one cached TTL configured value for A/AAAA glue records. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client A/AAAA query can cause Unbound to overwrite the cached expired parent-side glue rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client query is required since Unbound implicitly performs that query. This is a variant of CVE-2026-40622 which only addressed the NS query.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity low, availability none.

Weakness class

CVE-2026-42955 is classified as CWE-672: Operation on a Resource after Expiration or Release. A resource is used after it has been released or has expired.

Affected software

CVE-2026-42955 is recorded against 1 package.

  • unbound (from 1.16.2 up to 1.25.2)

Timeline and source

Published on 22 July 2026 and last revised on 24 July 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

www.nlnetlabs.nl

Details

Severity LOW
CVSS Score 3.7
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
CWE CWE-672
Public Exploit ✅ No
Source NVD
Published 2026-07-22
Updated 2026-08-11
Modified 2026-07-24
Fix URL N/A

Affected Packages

Software From version Fixed in
unbound 1.16.2 1.25.2

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