CVE-2026-23527H3 is a minimal H(TTP) framework built for high performance and portability.
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No exploitation reported and no EPSS estimate yet.
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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
- 9.8 CRITICAL (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-444
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Modified
- Record last updated
- Jun 17, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
h3 h3 h3:h3 | before 1.15.5 | NVD |
References
- https://github.com/h3js/h3/commit/618ccf4f37b8b6148bea7f36040471af45bfb097patch
- https://github.com/h3js/h3/releases/tag/v1.15.5
- https://github.com/h3js/h3/security/advisories/GHSA-mp2g-9vg9-f4cgexploit, vendor-advisory
- https://simonkoeck.com/writeups/h3-transfer-encoding-request-smuggling
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.