Vulnerability · Published Jan 15, 2026 · Assigned by GitHub_M

CVE-2026-23527h3 v1 has Request Smuggling (TE.TE) issue

High 8.9

In plain English

A high-severity security flaw in h3 from h3js. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 50% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.9High

Exploit odds (30 days)0.6%top 49.8% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	h3	1.15.5	GHSA-mp2g-9vg9-f4cg

Affected products (as reported)

Vendor	Product	Versions
h3js	h3	< 1.15.5

Weakness: CWE-444 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L

References

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