CVE-2026-23527

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.

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