CVE-2026-23527

Published: Jan 15, 2026Modified: Jun 17, 2026

9.8

Vector

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

Exploitability: 3.9 / Impact: 5.9

Source: NVD

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.

Affected (1)

Products: H3: H3

1 product

Configuration A

1 vulnerable

Vulnerable Software	Affected Versions
H3 H3	Before 1.15.5

Related CWEs

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.

References (4)

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

Source: security-advisories@github.com

Patch

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

Source: security-advisories@github.com

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

Source: security-advisories@github.com

ExploitVendor Advisory

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

Source: security-advisories@github.com

Timeline

No history available yet.