CVE-2026-42960

Medium

Published: 20 May 2026

Published

20 May 2026

Modified

20 May 2026

KEV Added

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Patch

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CVSS Score v4 5.7 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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber

EPSS Score 0.0025 16.2th percentile

Risk Priority 35 floored blend · peak EPSS

Summary

CVE-2026-42960 is a medium-severity Acceptance of Extraneous Untrusted Data With Trusted Data (CWE-349) vulnerability in Nlnetlabs Unbound. Its CVSS base score is 5.7 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 16.2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2026-31083

Vulnerability details

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.

CWE(s): CWE-349

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1557.001 Name Resolution Poisoning and SMB Relay Credential Access

By responding to LLMNR/NBT-NS/mDNS network traffic, adversaries may spoof an authoritative source for name resolution to force communication with an adversary controlled system.

attack.mitre.org →

Why these techniques?

Vulnerability enables cache poisoning of public DNS resolver via spoofed/fragmented packets (T1190) and directly facilitates name resolution poisoning (T1557.001).

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0