CVE-2026-42960: Possible cache poisoning via promiscuous records for the authority section
Last updated 2 June 2026
Other sources
NLnet Labs Unbound up to and including version 1.25.0 is vulnerable to poisoning via promiscuous records for the authority section. Promiscuous RRSets that complement DNS replies in the authority section can be used to trick Unbound to cache such records. If an adversary is able to attach such records in a reply (i.e., spoofed packet, fragmentation attack) he would be able to poison Unbound's cache. A malicious actor can exploit the possible poisonous effect by injecting RRSets other than NS that are also accompanied by address records in a reply, for example MX. This could be achieved by trying to spoof a reply packet or fragmentation attacks. Unbound would then accept the relative address records in the additional section and cache them if the authority RRSet has enough trust at this point, i.e., in-zone data for the delegation point. Unbound 1.25.1 contains a patch with a fix that disregards address records from the additional section if they are not explicitly relevant only to authority NS records, mitigating the possible poison effect. This is a complement fix to CVE-2025-11411.
— Launchpad
Possible cache poisoning via promiscuous records for the authority section
— Microsoft
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
debian/unboundto a version that resolves this vulnerability.Fixed in 1.22.0-2+deb13u3Fixed in 1.25.1-1 - Upgrade
Upgrade
NLnet Labs Unboundto a version that resolves this vulnerability.Fixed in 1.25.1 - Compensating control
If upgrading is not immediately possible, mitigate by preventing spoofed or fragmented DNS replies from reaching Unbound (e.g., ensure network/firewall protections block off-path spoofing and DNS traffic that cannot be validated).
Event History
Frequently Asked Questions
What is the severity of CVE-2026-42960?
CVE-2026-42960 has been classified as a high severity vulnerability affecting certain versions of NLnet Labs Unbound.
How do I fix CVE-2026-42960?
To mitigate CVE-2026-42960, upgrade NLnet Labs Unbound to version 1.26.0 or later.
What kind of attack does CVE-2026-42960 enable?
CVE-2026-42960 enables cache poisoning attacks through promiscuous records in the authority section of DNS responses.
Which versions of NLnet Labs Unbound are affected by CVE-2026-42960?
CVE-2026-42960 affects NLnet Labs Unbound versions up to and including 1.25.0.
Is there a workaround for CVE-2026-42960 if I cannot upgrade?
Currently, there are no known workarounds for CVE-2026-42960 other than upgrading the software.