Memory Accounting Bypass Vulnerability in NLnet Labs Unbound DNS Resolver
CVE-2026-32665

7.5HIGH

Key Information:

Vendor

Nlnet Labs

Status
Unbound
Vendor
CVE Published:
22 July 2026

What is CVE-2026-32665?

A remote availability issue has been identified in NLnet Labs Unbound versions 1.22.0 through 1.25.1. When using DNS-over-QUIC (DoQ), the first two bidirectional streams in a QUIC connection circumvent the 'quic-size' gate, permitting large input buffers to be allocated incorrectly. This flaw enables an attacker to exceed the configured 'quic-size' limit, resulting in a denial of service for downstream DoQ clients if Unbound is built with DoQ support and is set up with a configured 'quic-port'. By exploiting this vulnerability, a malicious remote client can effectively disrupt service and degrade performance without significant resource expenditure.

Affected Version(s)

Unbound 1.22.0 < 1.25.2

References

https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-32665...
vendor-advisory

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

N0zoM1z0 (GitHub user)
Kunta Chu (Tsinghua University)
Kaihua Wang (Tsinghua University)
Jianjun Chen (Tsinghua University)
Qifan Zhang (Palo Alto Networks)
Xuanchao Xie
.