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 is 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 during processing. This results in degradation of service or denial of service. The issue is addressed in Unbound 1.25.1 by introducing a limit of 100 acceptable incoming EDNS options, preventing excessive resource consumption.
Potential Impact
Successful exploitation can cause degradation or denial of service on affected Unbound DNS resolvers by exhausting processing threads through parsing overhead. There is no indication of privilege escalation, data leakage, or remote code execution. The impact is limited to service availability degradation.
Mitigation Recommendations
Upgrade to Unbound version 1.25.1 or later, which contains an official fix limiting the number of acceptable incoming EDNS options to 100. This patch effectively mitigates the vulnerability. No other mitigation guidance is provided or required.
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).
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-41292 is 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 during processing. This results in degradation of service or denial of service. The issue is addressed in Unbound 1.25.1 by introducing a limit of 100 acceptable incoming EDNS options, preventing excessive resource consumption.
Potential Impact
Successful exploitation can cause degradation or denial of service on affected Unbound DNS resolvers by exhausting processing threads through parsing overhead. There is no indication of privilege escalation, data leakage, or remote code execution. The impact is limited to service availability degradation.
Mitigation Recommendations
Upgrade to Unbound version 1.25.1 or later, which contains an official fix limiting the number of acceptable incoming EDNS options to 100. This patch effectively mitigates the vulnerability. No other mitigation guidance is provided or required.
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
Threat ID: 6a0d86fdba1db4736270ee60
Added to database: 5/20/2026, 10:03:41 AM
Last enriched: 5/20/2026, 10:19:56 AM
Last updated: 5/20/2026, 1:37:58 PM
Views: 3
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
External Links
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.