---
title: "CVE-2026-69210: Http4s - Denial of Service"
description: "Http4s < 0.23.35 and < 1.0.0-M47 contain a denial of service caused by improper handling of negative 64-bit WebSocket frame lengths in FrameTranscoder.bodyLength, letting remote clients cause infinite decode loops and resource exhaustion, exploit requires completing a WebSocket handshake through Ember server."
url: https://panop.io/threat-heartbeat/CVE-2026-69210/
---

# CVE-2026-69210 Http4s - Denial of Service

Http4s < 0.23.35 and < 1.0.0-M47 contain a denial of service caused by improper handling of negative 64-bit WebSocket frame lengths in FrameTranscoder.bodyLength, letting remote clients cause infinite decode loops and resource exhaustion, exploit requires completing a WebSocket handshake through Ember server.

CVSS base score 7.5 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.63% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-69210)

## Details

Type

Denial of Service

Impact

Denial Of Service

CVSS vector

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

Published

15 September 2026

Updated

15 October 2026

Weakness

[CWE-835](https://cwe.mitre.org/data/definitions/835.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-2026-69210](https://nvd.nist.gov/vuln/detail/CVE-2026-69210)
- [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-3j86-pj9g-jchr](https://github.com/http4s/http4s/security/advisories/GHSA-3j86-pj9g-jchr)
- [https://github.com/http4s/http4s/commit/c7d3ef90dc2ed1cd464968ab1b34f2f1762ddae2](https://github.com/http4s/http4s/commit/c7d3ef90dc2ed1cd464968ab1b34f2f1762ddae2)

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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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