# CVE-2026-69204

## Summary

- **CVE ID:** CVE-2026-69204
- **Severity:** CRITICAL
- **CVSS Score:** 9.2 (CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N)
- **CWE:** CWE-444
- **Published:** Sep 15, 2026
- **Last Modified:** Sep 15, 2026

## Description

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/1.1 does not reject messages containing both Transfer-Encoding and Content-Length, so an intermediary and Ember can select different body framing rules. When ember-server is behind a keep-alive intermediary that forwards both headers and frames by Content-Length, an unauthenticated attacker can smuggle a second request, bypass intermediary access controls, poison caches, or cause a victim request to be joined to an attacker-controlled prefix. The shared response parser can also desynchronize an ember-client connection when a malicious or compromised upstream sends both headers. This issue is fixed in versions 0.23.35 and 1.0.0-M47.

## Affected Products

- http4s — http4s (< 0.23.35)
- http4s — http4s (>= 1.0.0-M1, < 1.0.0-M47)

## References

- [CNA](https://github.com/http4s/http4s/security/advisories/GHSA-8h4c-x2wg-6xp8)
- [CNA](https://github.com/http4s/http4s/commit/9feaf8677951a52af906ae9664ff6f0543d9d810)
- [CNA](https://github.com/http4s/http4s/releases/tag/v0.23.35)
- [CNA](https://github.com/http4s/http4s/releases/tag/v1.0.0-M47)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.33%
- **EPSS Percentile:** 26.2

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-17._