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.
Scores
CVSS v3
8.9
EPSS
0.0004
EPSS Percentile
10.8%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
no
Technical Impact
total
Details
CWE
CWE-444
Status
published
Products (3)
h3/h3
< 1.15.5
h3js/h3
< 1.15.5
npm/h3
0 - 1.15.5npm
Published
Jan 15, 2026
Tracked Since
Feb 18, 2026