CVE-2026-23527

h3 v1 has Request Smuggling (TE.TE) issue

CVSS 8.9 HIGHEPSS 0.6%CWE-444

Vexday Risk Score

21Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 8.9EPSS 0.6%KEV nãoPoC —Nuclei —Metasploit —Patch —

Lifecycle

15 Jan 2026Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

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:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L

Affected products

h3js · h3

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References

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