CVE-2026-42955
LOWDescription
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 to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N/E:U
Exploit Intelligence
Low risk: more likely to be exploited than 10% of all known CVEs.
References
Related Vulnerabilities
Other CWE-672 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2024-23638 | Medium | 6.5 | 60% | - | Fix |
| CVE-2020-11027 | Medium | 6.1 | 14% | - | Fix |
| CVE-2019-17638 | Critical | 9.4 | 11% | - | Fix |
| CVE-2009-3547 | High | 7.0 | 4.9% | - | - |
| CVE-2019-15691 | High | 7.2 | 4.7% | - | Fix |
| CVE-2020-24030 | Critical | 9.8 | 2.7% | - | - |
Common questions
How do I fix CVE-2026-42955?
Published advisories record a fix for 3 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2026-42955 being actively exploited?
Not that we know of. CVE-2026-42955 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.20% is the estimated probability that it will be exploited in the next 30 days. That is higher than 10% of all scored CVEs.
How severe is CVE-2026-42955?
CVE-2026-42955 has a CVSS v3 base score of 3.7, rated low. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-42955 affect?
Published advisories record a fix for unbound (Debian), unbound (Red Hat / RHEL), unbound (Rocky). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-24.