CVE-2026-81634 (High) detected in src4.0.4 #537

Vulnerable Library - src4.0.4

MidnightBSD OS source code

Library home page: https://github.com/MidnightBSD/src.git

Found in base branches: stable/4.0, master

Vulnerable Source Files (1)

/contrib/unbound/validator/val_sigcrypt.c

Vulnerability Details

In NLnet Labs Unbound up to and including 1.26.0, a 255 length query name with a large TCP response can lead to a heap buffer overflow during the RRSet canonicalisation routine. This is caused by missing to add the first owner name into the buffer length check. A malicious actor operating a malicious name server or tampering with an incoming response to Unbound (canonicalisation happens before DNSSEC validation), can trigger the vulnerability.

Publish Date: 2026-09-16

URL: CVE-2026-81634

CVSS 3 Score Details (7.5)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: Low
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
• Impact Metrics:
  • Confidentiality Impact: None
  • Integrity Impact: None
  • Availability Impact: High