# CVE-2025-8671: varnish: A mismatch caused by client-triggered server-sent stream resets between HTTP/2 specifications and the internal archit...

CVE-2025-8671 is fixed in 2 products on 1 platform, first by dnsdist 1.8.3-2ubuntu0.1~esm1, released August 13, 2025. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2025-8671
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0364
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 13, 2025

## Description

A mismatch caused by client-triggered server-sent stream resets between HTTP/2 specifications and the internal architectures of some HTTP/2 implementations may result in excessive server resource consumption leading to denial-of-service (DoS).  By opening streams and then rapidly triggering the server to reset them—using malformed frames or flow control errors—an attacker can exploit incorrect stream accounting. Streams reset by the server are considered closed at the protocol level, even though backend processing continues. This allows a client to cause the server to handle an unbounded number of concurrent streams on a single connection. This CVE will be updated as affected product details are released.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | dnsdist Ubuntu 24.04.5 LTS (noble) | 1.8.3-2ubuntu0.1~esm1 | [dnsdist 1.8.3-2ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-dnsdist-1.8.3-2ubuntu0.1-esm1.md) | Aug 13, 2025 |
| Linux | dnsdist Ubuntu 25.10 (questing) | 1.9.10-1ubuntu0.1 | [dnsdist 1.9.10-1ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-questing-dnsdist-1.9.10-1ubuntu0.1.md) | Sep 18, 2025 |
| Linux | dnsdist opensuse-leap 16.0 | 1.9.11-160000.1.1 | [OPENSUSE-SU-2026:20461-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20461-1.md) | Apr 2, 2026 |
| Linux | dnsdist sles 15.7 | 1.9.11-150700.3.6.1 | [SUSE-SU-2026:0888-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0888-1.md) | Mar 13, 2026 |
| Linux | dnsdist sles 16.0 | 1.9.11-160000.1.1 | [SUSE-SU-2026:20995-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-20995-1.md) | Apr 2, 2026 |
| Linux | varnish Debian 13.5 (trixie) | 7.7.0-3+deb13u1 | [DEBIAN-CVE-2025-8671](https://patchblox.com/security/data/fix/linux/debian-cve-2025-8671.md) | Aug 13, 2025 |
| Linux | varnish opensuse-leap 16.0 | 7.7.3-bp160.1.1 | [OPENSUSE-SU-2026:22131-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-22131-1.md) | Nov 7, 2026 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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