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CVE-2026-23527

Published: Jan 15, 2026

Modified: Apr 13, 2026

PUBLISHED

CVSS v3.1

8.9

HIGH

Description

H3 is a minimal H(TTP) framework built for high performance and portability. Prior to 1.15.5, there is a critical HTTP Request Smuggling vulnerability. readRawBody is doing a strict case-sensitive check for the Transfer-Encoding header. It explicitly looks for "chunked", but per the RFC, this header should be case-insensitive. This vulnerability is fixed in 1.15.5.

Vendor	Product	Versions
h3js	h3	affected `< 1.15.5`

Weaknesses (CWE)

CVSS v3.1 Details

CVSS v3.1 Vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

Low

References

https://github.com/h3js/h3/security/advisories/GHSA-mp2g-9vg9-f4cg

x_refsource_CONFIRM

https://github.com/h3js/h3/commit/618ccf4f37b8b6148bea7f36040471af45bfb097

x_refsource_MISC

https://github.com/h3js/h3/releases/tag/v1.15.5

x_refsource_MISC

https://simonkoeck.com/writeups/h3-transfer-encoding-request-smuggling

x_refsource_MISC

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