Denial of Service and Remote Code Execution Vulnerability in Unbound DNS Resolver by NLnet Labs
CVE-2026-81642

9.1CRITICAL

Key Information:

Vendor

Nlnet Labs

Status
Unbound
Vendor
CVE Published:
16 September 2026

What is CVE-2026-81642?

A vulnerability in NLnet Labs' Unbound DNS resolver enables attackers to exploit DNSKEY records, potentially leading to denial of service and remote code execution. The flaw arises from a buffer overflow that can occur when a DNSKEY is crafted to include an owner compression pointer referencing its own RDATA. By querying a vulnerable Unbound instance with maliciously formed DNSKEYs, an adversary can take control, thereby executing arbitrary code and jeopardizing system integrity.

Affected Version(s)

Unbound 0 < 1.26.1

References

https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-81642...
vendor-advisory

CVSS V4

Score:
9.1
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Yuqi Qiu (Nankai University, AOSP Lab)
Xiang Li (Nankai University, AOSP Lab)
.