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.
在 2.0.1-rc.18 之前版本的 h3 中， 和 函数未正确校验从用户可控的 Cookie 值中解析出的分块数量（chunk count）。攻击者可发送一个精心构造的 Cookie 头，其中包含一个极大的分块数量，从而触发 O(n²) 的清理循环，导致服务器进程挂起。
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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
Affected Products
II. Public POCs for CVE-2026-86250
| # | POC Description | Source Link | Shenlong Link |
|---|
AI-Generated POC
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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
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CVE-2026-86253
h3 before 1.15.6 Path Traversal via Percent-Encoded Dot Segm -
CVE-2026-86252
h3 before 1.15.9 SSE Event Injection via Carriage Return -
CVE-2026-86251
h3 before 1.15.9 Path Traversal via Double Decoding -
CVE-2026-86205
h3 before 2.0.1-rc.18 Open Redirect via redirectBack() -
CVE-2026-33490
h3: Missing Path Segment Boundary Check in `mount()` Causes
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CVE-2026-86253
h3 before 1.15.6 Path Traversal via Percent-Encoded Dot Segm -
CVE-2026-86252
h3 before 1.15.9 SSE Event Injection via Carriage Return -
CVE-2026-86251
h3 before 1.15.9 Path Traversal via Double Decoding -
CVE-2026-86205
h3 before 2.0.1-rc.18 Open Redirect via redirectBack() -
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V. Comments for CVE-2026-86250
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