CVE-2026-23527

CRITICAL EPSS 43.2%
Published Jan 15, 20265mo ago · Modified Jun 17, 20262w ago
9.8 CVSS 3.1
Critical
Find Similar
Published Jan 15, 2026 5mo ago
Last Modified Jun 17, 2026 2w ago

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.

CVSS Details

Base Score
9.8
Exploitability
3.9
Impact
5.9
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope Unchanged
Confidentiality High
Integrity High
Availability High

Threat Intelligence

EPSS Exploit Probability
43.2% percentile
Exploit & Patch Status
Public Exploit Known
Patch Available

Weaknesses 1

CWE-444

Affected Products 1

VendorProductVersionRange
h3h3* <1.15.5

References 4

  • github.com https://github.com/h3js/h3/commit/618ccf4f37b8b6148bea7f36040471af45bfb097
    Patch
  • github.com https://github.com/h3js/h3/releases/tag/v1.15.5
  • github.com https://github.com/h3js/h3/security/advisories/GHSA-mp2g-9vg9-f4cg
    ExploitVendor Advisory
  • simonkoeck.com https://simonkoeck.com/writeups/h3-transfer-encoding-request-smuggling

Remediation

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