Home/CVE/H3 is a minimal H(TTP) framework built for high performance and portability. Prior to 1.15.5, there is a critical HTTP R
CVE

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 R

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.

HIGH · CVSS 8.9 EPSS 0.00043
Act now
  • Public exploit or PoC is available
  • CVSS base score ≥ 7.0
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
▤

Affected Products & Versions

1
h3< 1.15.5
▤

Affected Packages

1
Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
npm h3 HIGH fixed in 1.15.5
⚠

Public Exploits & PoCs

1
pocgithub.com · GHSA-mp2g-9vg9-f4cggithub.com
▣

Scoring & Timeline

8.9
HIGH · CVSS v3.1 · security-advisories@github.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD15 Jan 2026 · 08:16 PM
CVSS VectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
no
Technical impact
total
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
🔗

References & Sources

3
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://github.com/h3js/h3/commit/618ccf4f37b8b6148bea7f36040471af45bfb097Patch
https://github.com/h3js/h3/releases/tag/v1.15.5
https://simonkoeck.com/writeups/h3-transfer-encoding-request-smuggling
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