Performance Degradation Vulnerability in Unbound by NLnet Labs
CVE-2026-96405

5.3MEDIUM

Key Information:

Vendor

Nlnet Labs

Status
Unbound
Vendor
CVE Published:
21 October 2026

What is CVE-2026-96405?

The Unbound DNS resolver, developed by NLnet Labs, has a performance degradation vulnerability that arises from its handling of chained compression pointers. Specifically, while the software imposes limits on compression-pointer traversal for individual domain-name operations, it fails to establish an overall limit on the total inbound decompression workload. This oversight enables a malicious actor with recursive-query access to exploit specially crafted DNS replies. Such an attack can lead to excessive CPU usage, thereby significantly impacting the performance of the Unbound resolver during its operation.

Affected Version(s)

Unbound 0 < 1.26.2

References

https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-96405...
vendor-advisory

CVSS V3.1

Score:
5.3
Severity:
MEDIUM
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

Yuheng Zhang (Tsinghua University & Jingxian Technology Co., Ltd.)
Jianjun Chen (Tsinghua University)
Zihan Wang (Z.AI Co., Ltd.)
Kaiwen Shen (CloudItera)
.