Assertion in libngtcp2 when under pressure in high concurrency DNS-over-QUIC environments
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.
Problem Types
| Type | CWE ID | Description |
|---|
| CWE | CWE-617 | CWE-617: Reachable Assertion |
Type: CWE
Description: CWE-617: Reachable Assertion
Metrics
| Version | Base score | Base severity | Vector |
|---|
| 3.1 | 5.9 | MEDIUM | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H |
Version: 3.1
Base score: 5.9
Base severity: MEDIUM
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Timeline
| Event | Date |
|---|
| Issue reported by Kunta Chu | 2026-05-08 00:00:00 |
| NLnet Labs shares patch with Kunta Chu | 2026-07-02 00:00:00 |
| Kunta Chu verifies patch | 2026-07-03 00:00:00 |
| Fixes released with version 1.25.2 | 2026-07-22 00:00:00 |
Event: Issue reported by Kunta Chu
Date: 2026-05-08 00:00:00
Event: NLnet Labs shares patch with Kunta Chu
Date: 2026-07-02 00:00:00
Event: Kunta Chu verifies patch
Date: 2026-07-03 00:00:00
Event: Fixes released with version 1.25.2
Date: 2026-07-22 00:00:00