CVE-2025-8671: Fastly h20

High severity, CVSS 7.5. EPSS: 3.7% chance of exploitation in the next 30 days.

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.

Affected products

  • Fastly h20: version 579ecfa only
  • Suse Linux Enterprise Desktop: from 15 SP6, before 15 SP7 (fixed in 15 SP7)
  • Suse Linux Enterprise High Performance Computing: from 15 SP3, before 15 SP7 (fixed in 15 SP7)
  • Suse Linux Enterprise High Performance Computing Hpc: from 15, before 15 SP5 (fixed in 15 SP5)
  • Suse Linux Enterprise Module For Dev Tools: from 15 SP3, before 15 SP7 (fixed in 15 SP7)
  • Suse Linux Enterprise Module For Development Tools: from 15 SP2, before 15-SP5 (fixed in 15-SP5)
  • Suse Linux Enterprise Module For Package Hub: from 15 SP5, before 15 SP7 (fixed in 15 SP7)
  • Suse Linux Enterprise Server: from 12 SP5, before 15 SP7 (fixed in 15 SP7)
  • Suse Linux Enterprise Server For SAP Applications: from 15 SP6, before 15 SP7 (fixed in 15 SP7)
  • Suse Linux Opensuse Leap: version 15.6 only
  • Suse Linux Suse Manager Proxy: version 4.3 only
  • Suse Linux Suse Manager Retail Branch Server: version 4.3 only
  • Suse Linux Suse Manager Server: version 4.3 only
  • Suse Linux Suse Manager Server LTS: version 4.3 only
  • Varnish Software Varnish Cache: from 6.0LTS, up to and including 6.014; from 5, up to and including 7.71
  • Varnish Software Varnish Enterprise: from 6.0, up to and including 6.0.14r4
  • Wind River Linux

Published 2025-08-13. Last modified 2026-06-17.