---
title: "CVE-2026-69217: Http4s - HTTP Request Smuggling"
description: "Http4s prior to 0.23.35 and 1.0.0-M47 contains an HTTP request smuggling vulnerability caused by accepting differing duplicate Content-Length headers and using the last value, letting unauthenticated attackers bypass front-end controls and poison caches, exploit requires attacker to send crafted CL.CL requests."
url: https://panop.io/threat-heartbeat/CVE-2026-69217/
---

# CVE-2026-69217 Http4s - HTTP Request Smuggling

Http4s prior to 0.23.35 and 1.0.0-M47 contains an HTTP request smuggling vulnerability caused by accepting differing duplicate Content-Length headers and using the last value, letting unauthenticated attackers bypass front-end controls and poison caches, exploit requires attacker to send crafted CL.CL requests.

CVSS base score 8.7 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.50% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-69217)

## Details

Type

HTTP Request Smuggling

Impact

Man In The Middle

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N

Published

15 September 2026

Updated

15 October 2026

Weakness

[CWE-444](https://cwe.mitre.org/data/definitions/444.html)

## Vendor fix

Upgrade to versions 0.23.35 or 1.0.0-M47 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-69217](https://nvd.nist.gov/vuln/detail/CVE-2026-69217)
- [https://github.com/http4s/http4s/commit/24e8d34e3ea89f8f23e0053ec9944f6467e8086d](https://github.com/http4s/http4s/commit/24e8d34e3ea89f8f23e0053ec9944f6467e8086d)
- [https://github.com/http4s/http4s/releases/tag/v0.23.35](https://github.com/http4s/http4s/releases/tag/v0.23.35)
- [https://github.com/http4s/http4s/releases/tag/v1.0.0-M47](https://github.com/http4s/http4s/releases/tag/v1.0.0-M47)
- [https://github.com/http4s/http4s/security/advisories/GHSA-p83c-4wj9-p6w9](https://github.com/http4s/http4s/security/advisories/GHSA-p83c-4wj9-p6w9)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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