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CVE-2026-86250— h3 before 2.0.1-rc.18 Denial of Service via Unbounded Chunked Cookie

Quick assessment

Affected
h3js h3
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

H3是H3组织开源的一个HTTP框架。 H3 2.0.1-rc.18之前版本存在资源管理错误漏洞，该漏洞源于setChunkedCookie()和deleteChunkedCookie()函数对用户可控cookie值解析的chunk count验证不足，可能导致攻击者发送特制cookie头触发O(n²)清理循环，导致服务器进程挂起。

CVSS 7.5 · High EPSS 0.49% · P41

Affected Version Matrix 2

VendorProduct Version RangeStatus
h3js h3 2.0.0-beta.4< 2.0.1-rc.18 affected
2.0.1-rc.18 unaffected
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I. Basic Information for CVE-2026-86250

Vulnerability Information
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Vulnerability Title
h3 before 2.0.1-rc.18 Denial of Service via Unbounded Chunked Cookie
Source: CVE Program / CVE List V5
Vulnerability Description
h3 versions before 2.0.1-rc.18 fail to validate the chunk count parsed from user-controlled cookie values in setChunkedCookie() and deleteChunkedCookie() functions. Attackers can send a crafted cookie header with an extremely large chunk count to trigger an O(n²) cleanup loop that hangs the server process.
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
H3 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
H3是H3组织开源的一个HTTP框架。 H3 2.0.1-rc.18之前版本存在资源管理错误漏洞，该漏洞源于setChunkedCookie()和deleteChunkedCookie()函数对用户可控cookie值解析的chunk count验证不足，可能导致攻击者发送特制cookie头触发O(n²)清理循环，导致服务器进程挂起。
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
h3js h3 2.0.0-beta.4 ~ 2.0.1-rc.18 -

II. Public POCs for CVE-2026-86250

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III. Intelligence Information for CVE-2026-86250

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Vendor Advisories for CVE-2026-86250 (2)

Same Patch Batch · h3js · 2026-09-06 · 5 CVEs total

CVE-2026-86251 5.9 MEDIUM h3 before 1.15.9 Path Traversal via Double Decoding
CVE-2026-86253 5.9 MEDIUM h3 before 1.15.6 Path Traversal via Percent-Encoded Dot Segments
CVE-2026-86205 5.4 MEDIUM h3 before 2.0.1-rc.18 Open Redirect via redirectBack()
CVE-2026-86252 5.3 MEDIUM h3 before 1.15.9 SSE Event Injection via Carriage Return

IV. Related Vulnerabilities

Same product: h3
Same vendor: h3js
Same weakness: CWE-400

V. Comments for CVE-2026-86250

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