CVE-2026-41292: CWE-407: Inefficient Algorithmic Complexity in NLnet Labs Unbound
NLnet Labs Unbound up to and including version 1.25.0 is vulnerable to a degradation of service attack related to parsing long lists of incoming EDNS options. An adversary sending queries with too many EDNS options can hold Unbound threads hostage while they are parsing and creating internal data structures for the options. Coordinated attacks can result in degradation and/or denial of service. Unbound 1.25.1 contains a patch with a fix to limit acceptable incoming EDNS options (100).
AI Analysis
Technical Summary
CVE-2026-41292 describes an algorithmic complexity vulnerability in NLnet Labs Unbound DNS resolver up to version 1.25.0. The vulnerability arises from inefficient parsing of long lists of EDNS options in incoming DNS queries. An attacker can exploit this by sending queries with an excessive number of EDNS options, causing Unbound threads to be held hostage while processing these options, resulting in degraded service or denial of service. The issue is addressed in Unbound version 1.25.1 by introducing a limit of 100 acceptable incoming EDNS options, preventing resource exhaustion.
Potential Impact
Exploitation of this vulnerability can lead to degradation of service or denial of service in affected Unbound DNS resolvers by exhausting processing threads through excessive EDNS options. This impacts availability of the DNS service but does not involve privilege escalation, code execution, or data confidentiality breaches.
Mitigation Recommendations
A fix is available in Unbound version 1.25.1, which limits the number of acceptable incoming EDNS options to 100. Users should upgrade to version 1.25.1 or later to remediate this vulnerability. No other specific mitigations are indicated by the vendor advisory.
CVE-2026-41292: CWE-407: Inefficient Algorithmic Complexity in NLnet Labs Unbound
Description
NLnet Labs Unbound up to and including version 1.25.0 is vulnerable to a degradation of service attack related to parsing long lists of incoming EDNS options. An adversary sending queries with too many EDNS options can hold Unbound threads hostage while they are parsing and creating internal data structures for the options. Coordinated attacks can result in degradation and/or denial of service. Unbound 1.25.1 contains a patch with a fix to limit acceptable incoming EDNS options (100).
CVSS v4.0
Score 6.6medium
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-41292 describes an algorithmic complexity vulnerability in NLnet Labs Unbound DNS resolver up to version 1.25.0. The vulnerability arises from inefficient parsing of long lists of EDNS options in incoming DNS queries. An attacker can exploit this by sending queries with an excessive number of EDNS options, causing Unbound threads to be held hostage while processing these options, resulting in degraded service or denial of service. The issue is addressed in Unbound version 1.25.1 by introducing a limit of 100 acceptable incoming EDNS options, preventing resource exhaustion.
Potential Impact
Exploitation of this vulnerability can lead to degradation of service or denial of service in affected Unbound DNS resolvers by exhausting processing threads through excessive EDNS options. This impacts availability of the DNS service but does not involve privilege escalation, code execution, or data confidentiality breaches.
Mitigation Recommendations
A fix is available in Unbound version 1.25.1, which limits the number of acceptable incoming EDNS options to 100. Users should upgrade to version 1.25.1 or later to remediate this vulnerability. No other specific mitigations are indicated by the vendor advisory.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- NLnet Labs
- Date Reserved
- 2026-05-07T10:13:43.992Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
- Vendor Advisory Urls
- [{"url":"https://access.redhat.com/security/cve/CVE-2026-41292","vendor":"Red Hat"}]
Threat ID: 6a0d86fdba1db4736270ee60
Added to database: 05/20/2026, 10:03:41 UTC
Last enriched: 07/30/2026, 21:57:09 UTC
Last updated: 07/31/2026, 21:26:44 UTC
Views: 55
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