CVEvulnerability

CVE-2026-54340

7.5 HIGH Published 2026-07-17 Modified 2026-08-05 Official page ↗
Status
Analyzed
Published
2026-07-17
Last modified
2026-08-05
Assigner
[email protected]
CVSS 3.1 ([email protected])
7.5 HIGH — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weaknesses
CWE-400, CWE-770

Description

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 9265bdd, there is an HTTP/2 state amplification issue that combines HPACK decompression amplification with Slowloris-style stream stalling. Amplified decoded header state can be retained by stalled HTTP/2 streams, and depending on the configuration, additional limits are needed to bound decoded header state and prevent attack. This issue has been fixed by commit 9265bdd.

Affected configurations

• h2o h2o (>= 2026-05-29 < 2026-06-04)

Related

Weakness · CWE (2)

  • CWE-400 Uncontrolled Resource Consumption weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling weakness

References