h3js h3 up to 1.15.4 HTTP Request readRawBody request smuggling

Summaryinfo

A vulnerability described as problematic has been identified in h3js h3 up to 1.15.4. The affected element is the function readRawBody of the component HTTP Request Handler. Such manipulation leads to request smuggling. This vulnerability is uniquely identified as CVE-2026-23527. The attack can be launched remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in h3js h3 up to 1.15.4 and classified as problematic. Affected by this issue is the function readRawBody of the component HTTP Request Handler. The manipulation with an unknown input leads to a request smuggling vulnerability. Using CWE to declare the problem leads to CWE-444. 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. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-23527 since 01/13/2026. The exploitation is known to be difficult. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details are known, but there is no available exploit.

Upgrading to version 1.15.5 eliminates this vulnerability.

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Productinfo

Vendor

• h3js

Name

• h3

Version

• 1.15.0
• 1.15.1
• 1.15.2
• 1.15.3
• 1.15.4

Website

• Product: https://github.com/h3js/h3/

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