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🛡️ CVE-2025-8671 on Ubuntu — dnsdist

⚪ Unknown ✅ No Known Exploit OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

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.

Distribution advisory

This page covers CVE-2025-8671 as tracked by Ubuntu, for the package dnsdist. The fix is available in version 1.9.10-1ubuntu0.1; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: High — total loss, or loss the attacker controls.

Affected software

UBUNTU-CVE-2025-8671 is recorded against 4 packages.

  • dnsdist (fixed in 1.9.10-1ubuntu0.1)
  • h2o
  • lighttpd
  • varnish

Timeline and source

Published on 13 August 2025 and last revised on 20 May 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

ubuntu.com (Report)
www.cve.org (Report)
kb.cert.org (Report)
galbarnahum.com (Report)
github.com (Report)
github.com (Report)
gitlab.isc.org (Report)
support2.windriver.com (Report)
varnish-cache.org (Report)
www.fastlystatus.com (Report)
www.suse.com (Report)
www.openwall.com (Report)
ubuntu.com (Advisory)

Other advisories for this package

dnsdist has other advisories on record. If you are patching this one, these are worth checking on the same host:

CVE-2025-8671 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2025-08-13
Updated 2026-08-20
Modified 2026-05-20
Fix URL N/A

Affected Packages

Software From version Fixed in
dnsdist — 1.9.10-1ubuntu0.1
h2o — —
lighttpd — —
varnish — —

Similar Threats

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