CVE-2026-54340
CVE-2026-54340 · h2o has HTTP/2 state amplification
This page contains facts from public vulnerability sources. Check the original advisory before updating.
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.
CVSS 7.5 · High · EPSS 0.5%
- Published
- Updated
Stack: system
Affected products and versions
h2o
- Versions
- < 9265bdd: Affected
No fix published
h2o Debian:12
- Versions
- 2.2.5+dfsg2-10
- 2.2.5+dfsg2-11
- 2.2.5+dfsg2-7
- 2.2.5+dfsg2-8
- 2.2.5+dfsg2-8.1
- 2.2.5+dfsg2-8.1~exp1
- 2.2.5+dfsg2-9
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
h2o Ubuntu:Pro:18.04:LTS
- Versions
- 2.2.3+dfsg-2
- 2.2.4+dfsg-1
- 2.2.4+dfsg-1build1
- 2.2.4+dfsg-1ubuntu0.1~esm2
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
h2o Ubuntu:Pro:20.04:LTS
- Versions
- 2.2.5+dfsg2-3
- 2.2.5+dfsg2-3build1
- 2.2.5+dfsg2-3ubuntu0.1~esm1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
h2o Ubuntu:Pro:22.04:LTS
- Versions
- 2.2.5+dfsg2-6
- 2.2.5+dfsg2-6.1
- 2.2.5+dfsg2-6.1ubuntu1
- 2.2.5+dfsg2-6.1ubuntu2
- 2.2.5+dfsg2-6.1ubuntu2+esm1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
h2o Ubuntu:24.04:LTS
- Versions
- 2.2.5+dfsg2-7
- 2.2.5+dfsg2-8
- 2.2.5+dfsg2-8.1ubuntu1
- 2.2.5+dfsg2-8.1ubuntu2
- 2.2.5+dfsg2-8.1ubuntu3
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
dnsdist Ubuntu:Pro:24.04:LTS
- Versions
- 1.8.0-1
- 1.8.2-1
- 1.8.2-2
- 1.8.2-3
- 1.8.3-1
- 1.8.3-2
- 1.8.3-2build1
- 1.8.3-2build2
- 1.8.3-2ubuntu0.1~esm1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published