Vulnerability in H3
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.
Vulnerability class: HTTP Request Smuggling
EPSS: 0.006 (44.1th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 8.9 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L.
Affected products
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
Frequently asked questions
- What is CVE-2026-23527?
- CVE-2026-23527 is a high-severity vulnerability in H3, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 8.9/10. Published 2026-01-15.
- How severe is CVE-2026-23527?
- High severity. CVSS v3 base score is 8.9 out of 10.