CVE-2026-96405: CWE-770: Allocation of Resources Without Limits or Throttling in NLnet Labs Unbound
Description
NLnet Labs Unbound versions prior to 1.26.2 have a vulnerability where excessive chained compression pointers in DNS messages can cause high CPU usage. This occurs because Unbound limits compression-pointer traversal per domain-name operation but lacks an aggregate inbound decompression-work budget. An attacker with recursive-query access and control over a delegated authority can exploit this to degrade Unbound's performance. The vulnerability has a medium severity with a CVSS score of 5.3 and does not impact confidentiality or integrity, only availability.
CVSS v3.1
Score 5.3medium
Affected software
NLnet Labs
Unbound
pkg:github/nlnetlabs/unboundRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-96405 describes a resource exhaustion vulnerability in NLnet Labs Unbound DNS resolver up to version 1.26.1. The software limits compression-pointer traversal on a per-domain basis but does not enforce an overall limit on decompression workload for incoming messages. Attackers controlling a delegated DNS authority and having recursive-query access can craft DNS replies with many chained compression pointers, causing excessive CPU consumption and degrading resolver performance. This vulnerability is classified under CWE-770 (Allocation of Resources Without Limits or Throttling).
Potential Impact
The vulnerability allows an attacker to degrade the availability of the Unbound DNS resolver by causing high CPU usage through specially crafted DNS responses. There is no impact on confidentiality or integrity. The attack requires recursive-query access and control over a delegated DNS authority to serve malicious replies.
Mitigation Recommendations
A fix is available in Unbound version 1.26.2. Users should upgrade to version 1.26.2 or later to remediate this vulnerability. No other mitigation guidance is provided.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- NLnet Labs
- Date Reserved
- 2026-10-14T09:16:14.093Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ad883832cdf04f656d82210
Added to database: 10/21/2026, 09:18:59 UTC
Last enriched: 10/21/2026, 09:33:50 UTC
Last updated: 10/21/2026, 13:40:20 UTC
Views: 8
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