CVE-2026-14586: CWE-617: Reachable Assertion in NLnet Labs Unbound
In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, in DNS-over-QUIC environments, with high concurrency and under pressure, an assertion in libngtcp2 about monotonic timestamps could trigger and result in server termination and thus denial of service. When interfacing with libngtcp2, for DNS-over-QUIC support in Unbound, it is expected to use monotonic time. Unbound was using realtime instead, and in DoQ environments with high concurrency and under pressure, an assert in libngtcp2 for the quic timestamp would trigger and terminate the server.This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces.
AI Analysis
Technical Summary
CVE-2026-14586 is a reachable assertion vulnerability in NLnet Labs Unbound DNS resolver when operating with DNS-over-QUIC support. The issue arises because Unbound incorrectly uses realtime instead of monotonic time for QUIC timestamps when interfacing with libngtcp2. Under conditions of high concurrency and pressure, this causes an assertion in libngtcp2 to trigger, terminating the server process and causing denial of service. The vulnerability affects Unbound versions starting from 1.22.0 through 1.25.1 when compiled with '--with-libngtcp2' and configured with 'quic-port'.
Potential Impact
Successful exploitation causes the Unbound server to terminate unexpectedly, resulting in denial of service. There is no impact on confidentiality or integrity. The vulnerability requires specific configuration (DoQ support enabled and quic-port configured) and high concurrency conditions to trigger.
Mitigation Recommendations
No official patch or fix has been confirmed as of the published date. Users should monitor the NLnet Labs advisories for updates. If DNS-over-QUIC support is not required, disabling or not compiling Unbound with '--with-libngtcp2' and not configuring 'quic-port' can avoid exposure. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance.
CVE-2026-14586: CWE-617: Reachable Assertion in NLnet Labs Unbound
Description
In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, in DNS-over-QUIC environments, with high concurrency and under pressure, an assertion in libngtcp2 about monotonic timestamps could trigger and result in server termination and thus denial of service. When interfacing with libngtcp2, for DNS-over-QUIC support in Unbound, it is expected to use monotonic time. Unbound was using realtime instead, and in DoQ environments with high concurrency and under pressure, an assert in libngtcp2 for the quic timestamp would trigger and terminate the server.This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces.
CVSS v3.1
Score 5.9medium
Affected software
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-2026-14586 is a reachable assertion vulnerability in NLnet Labs Unbound DNS resolver when operating with DNS-over-QUIC support. The issue arises because Unbound incorrectly uses realtime instead of monotonic time for QUIC timestamps when interfacing with libngtcp2. Under conditions of high concurrency and pressure, this causes an assertion in libngtcp2 to trigger, terminating the server process and causing denial of service. The vulnerability affects Unbound versions starting from 1.22.0 through 1.25.1 when compiled with '--with-libngtcp2' and configured with 'quic-port'.
Potential Impact
Successful exploitation causes the Unbound server to terminate unexpectedly, resulting in denial of service. There is no impact on confidentiality or integrity. The vulnerability requires specific configuration (DoQ support enabled and quic-port configured) and high concurrency conditions to trigger.
Mitigation Recommendations
No official patch or fix has been confirmed as of the published date. Users should monitor the NLnet Labs advisories for updates. If DNS-over-QUIC support is not required, disabling or not compiling Unbound with '--with-libngtcp2' and not configuring 'quic-port' can avoid exposure. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- NLnet Labs
- Date Reserved
- 2026-07-03T11:59:36.383Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a60c4209c2644c7f80e9121
Added to database: 07/22/2026, 13:22:40 UTC
Last enriched: 07/22/2026, 13:41:53 UTC
Last updated: 07/22/2026, 21:48:57 UTC
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.