Vulnerability 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 Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| H3 | H3 | < 1.15.5 |
Related Weaknesses (CWE)
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-f4cgExploitVendor Advisory
- https://simonkoeck.com/writeups/h3-transfer-encoding-request-smuggling
FAQ
What is CVE-2026-23527?
CVE-2026-23527 is a vulnerability with a CVSS score of 8.9 (HIGH). 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 che...
How severe is CVE-2026-23527?
CVE-2026-23527 has been rated HIGH with a CVSS base score of 8.9/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-23527?
Check the references section above for vendor advisories and patch information. Affected products include: H3 H3.