CVE-2026-97206: CWE-416: Use After Free in NLnet Labs Unbound
Description
NLnet Labs Unbound versions 1.22.0 through 1.26.1 contain a use-after-free vulnerability in the DNS-over-QUIC (DoQ) implementation. This flaw occurs during multi-threaded operation when a client-triggered QUIC path migration causes cleanup of a DoQ stream while a mesh reply still holds a pointer to it. The subsequent dereference of this freed pointer leads to a crash, impacting availability.
CVSS v3.1
Score 7.5high
Affected software
NLnet Labs
Unbound
Run 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-2026-97206 is a use-after-free vulnerability (CWE-416) in NLnet Labs Unbound's DNS-over-QUIC (DoQ) feature affecting versions 1.22.0 up to and including 1.26.1. The issue arises under multi-threaded operation when a remote DoQ client triggers a QUIC path migration that initiates stream and connection cleanup. During this cleanup, the DoQ stream is freed while a mesh reply still retains a pointer to it. When the mesh reply completes, it dereferences the stale pointer, causing a crash of the Unbound process.
Potential Impact
The vulnerability leads to a denial-of-service condition by crashing the Unbound DNS resolver when exploited. There is no indication of confidentiality or integrity impact. No known exploits are reported in the wild at this time.
Mitigation Recommendations
No patch links or vendor advisory details are provided, so patch status is not yet confirmed—check the vendor advisory for current remediation guidance. Until a fix is available, consider disabling DNS-over-QUIC or limiting exposure to untrusted DoQ clients to reduce risk.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- NLnet Labs
- Date Reserved
- 2026-10-14T09:16:14.090Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ad883832cdf04f656d82211
Added to database: 10/21/2026, 09:18:59 UTC
Last enriched: 10/21/2026, 09:33:14 UTC
Last updated: 10/21/2026, 09:34:06 UTC
Views: 16
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.