DNS Cache Poisoning Vulnerability in Unbound by NLnet Labs
CVE-2026-42960

5.7MEDIUM

Key Information:

Vendor

Nlnet Labs

Status
Unbound
Vendor
CVE Published:
20 May 2026

What is CVE-2026-42960?

Versions of Unbound up to and including 1.25.0 are susceptible to a DNS cache poisoning vulnerability due to improper handling of promiscuous records in the authority section. Malicious actors can exploit this vulnerability by inserting misleading DNS records, such as MX records, in reply packets. When Unbound receives these compromised records, it can unwittingly cache them based on their perceived authority, allowing attackers to manipulate DNS queries. The introduced fix in version 1.25.1 ensures that only relevant authority NS records are considered for caching, thereby mitigating the risk posed by this vulnerability.

Affected Version(s)

Unbound 0 < 1.25.1

References

https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42960...
vendor-advisory

CVSS V4

Score:
5.7
Severity:
MEDIUM
Confidentiality:
None
Integrity:
High
Availability:
None
Attack Vector:
Adjacent Network
Attack Complexity:
Low
Attack Required:
Physical
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

TaoFei Guo (Peking University)
Yang Luo (Tsinghua University)
JianJun Chen (Tsinghua University)
.