Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1336 CNY

100%
Buy Us a Coffee

CVE-2026-54340— h2o has HTTP/2 state amplification

CVSS 7.5 · High EPSS 0.28% · P20

Affected Version Matrix 1

VendorProductVersion RangeStatus
h2oh2o< 9265bddaffected
Get alerts for future matching vulnerabilitiesLog in to subscribe

I. Basic Information for CVE-2026-54340

Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
h2o has HTTP/2 state amplification
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5
Vulnerability Title
h2o 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
h2o是H2O公司开源的一款新一代HTTP服务器。 h2o 9265bdd之前版本存在资源管理错误漏洞，该漏洞源于HTTP/2状态放大问题，结合HPACK解压放大与Slowloris-style流停滞，导致解码后的标头状态被停滞的HTTP/2流保留，攻击者可通过网络利用此问题造成拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

VendorProductAffected VersionsCPESubscribe
h2oh2o < 9265bdd -

II. Public POCs for CVE-2026-54340

#POC DescriptionSource LinkShenlong Link
AI-Generated POCPremium
Qwen3.6-35B-A3B · 10225 chars
Pro+ exclusive includes:
Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
In-depth vulnerability mechanism
Trigger conditions & impact
Full executable POC code
Exploit chain & mitigation
POC zip download
100+ AI POC generations per month

III. Intelligence Information for CVE-2026-54340

请登录查看更多情报信息。

Patches & Fixes for CVE-2026-54340 (1)

Vendor Advisories for CVE-2026-54340 (1)

Same Patch Batch · h2o · 2026-07-16 · 7 CVEs total

CVE-2026-444367.5 HIGHQuicly is vulnerable to connection state corruption
CVE-2026-444357.5 HIGHQuicly: Remote Denial of Service via assertion failure when CRYPTO stream handshake data e
CVE-2026-444537.5 HIGHh2o is vulnerable to musl libc stack overflow
CVE-2026-444525.9 MEDIUMh2o is vulnerable to heap overrun
CVE-2026-444335.3 MEDIUMQuicly is vulnerable to memory exhaustion
CVE-2026-444345.3 MEDIUMQuicly is vulnerable to stateless reset injection

IV. Related Vulnerabilities

Same product: h2o
Same vendor: h2o
Same weakness: CWE-400

V. Comments for CVE-2026-54340

No comments yet

Leave a comment