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

Goal: 1000 CNY · Raised: 1359 CNY

100%
Buy Us a Coffee

CVE-2026-44435— Quicly: Remote Denial of Service via assertion failure when CRYPTO stream handshake data exceeds 32KB

Quick assessment

Affected
h2o quicly
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

H2O quicly是H2O公司开源的一个 IETF QUIC 协议的实现。 H2O quicly 937d0e9之前版本存在安全漏洞，该漏洞源于CRYPTO流中有效握手消息超过32KB时触发断言失败，导致拒绝服务。

CVSS 7.5 · High EPSS 0.49% · P40

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 1

VendorProduct Version RangeStatus
h2o quicly < 937d0e9 affected
Get alerts for future matching vulnerabilities Log in to subscribe

I. Basic Information for CVE-2026-44435

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Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.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
Quicly: Remote Denial of Service via assertion failure when CRYPTO stream handshake data exceeds 32KB
Source: CVE Program / CVE List V5
Vulnerability Description
Quicly is an IETF QUIC protocol implementation intended primarily for use within the H2O HTTP server. Prior to commit 937d0e9, an assertion failure is raised when the total number of valid handshake messages received over a CRYPTO stream of a single packet number space exceeds 32KB, causing a Denial of Service. This issue has been fixed by commit 937d0e9.
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
可达断言
Source: CVE Program / CVE List V5
Vulnerability Title
H2O quicly 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
H2O quicly是H2O公司开源的一个 IETF QUIC 协议的实现。 H2O quicly 937d0e9之前版本存在安全漏洞，该漏洞源于CRYPTO流中有效握手消息超过32KB时触发断言失败，导致拒绝服务。
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

Vendor Product Affected Versions CPE Subscribe
h2o quicly < 937d0e9 -

II. Public POCs for CVE-2026-44435

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 8466 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-2026-44435

请登录查看更多情报信息。

Patches & Fixes for CVE-2026-44435 (1)

Vendor Advisories for CVE-2026-44435 (1)

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

CVE-2026-44436 7.5 HIGH Quicly is vulnerable to connection state corruption
CVE-2026-44453 7.5 HIGH h2o is vulnerable to musl libc stack overflow
CVE-2026-54340 7.5 HIGH h2o has HTTP/2 state amplification
CVE-2026-44452 5.9 MEDIUM h2o is vulnerable to heap overrun
CVE-2026-44433 5.3 MEDIUM Quicly is vulnerable to memory exhaustion
CVE-2026-44434 5.3 MEDIUM Quicly is vulnerable to stateless reset injection

IV. Related Vulnerabilities

Same product: quicly
Same vendor: h2o
Same weakness: CWE-617

V. Comments for CVE-2026-44435

No comments yet

Leave a comment