---
id: CVE-2026-69213
title: Http4s is a Scala interface for HTTP services
summary: >-
  Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47,
  Ember HTTP/2 serializes outbound frames through one unbounded queue consumed
  by writeLoop. When the peer stops reading, an unauthenticated HTTP/2 client
  can c…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-400
  - CWE-770
vendor: http4s
product: http4s
affected:
  - http4s < 0.23.35
  - 'http4s >= 1.0.0-M1, < 1.0.0-M47'
patched:
  - 'org.http4s:http4s-ember-core_2.12 0.23.35'
  - 'org.http4s:http4s-ember-core_2.13 0.23.35'
  - 'org.http4s:http4s-ember-core_3 0.23.35'
  - 'org.http4s:http4s-ember-core_3 1.0.0-M47'
  - 'org.http4s:http4s-ember-core_2.13 1.0.0-M47'
published: '2026-09-15'
updated: '2026-09-17'
sourceUpdated: '2026-09-17T17:16:46.607'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-69213'
references:
  - url: >-
      https://github.com/http4s/http4s/commit/13fe24d6440bde2f1eb70121486cf59c278e6bae
    label: security-advisories@github.com
  - url: 'https://github.com/http4s/http4s/releases/tag/v0.23.35'
    label: security-advisories@github.com
  - url: 'https://github.com/http4s/http4s/releases/tag/v1.0.0-M47'
    label: security-advisories@github.com
  - url: 'https://github.com/http4s/http4s/security/advisories/GHSA-8f3q-3jmv-7prw'
    label: security-advisories@github.com
  - url: 'https://github.com/advisories/GHSA-8f3q-3jmv-7prw'
tags:
  - nvd
  - cve.org
  - ghsa
  - maven
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-17T16:42:58.154505Z'
epss: 0.0063
epssPercentile: 0.47963
aliases:
  - GHSA-8f3q-3jmv-7prw
ecosystem: maven
ingestedAt: '2026-09-15T19:42:58.804Z'
---

## Overview

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/2 serializes outbound frames through one unbounded queue consumed by writeLoop. When the peer stops reading, an unauthenticated HTTP/2 client can continue sending PING, SETTINGS, or DATA frames that cause Ember to enqueue acknowledgments or WINDOW_UPDATE frames faster than the writer drains them, exhausting heap memory on a server built with withHttp2. The shared behavior also affects an ember-client connected to a hostile HTTP/2 server, and the patch replaces the unbounded path with bounded, backpressured outbound queues. This issue is fixed in versions 0.23.35 and 1.0.0-M47.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-69213)

Affected packages:

- `org.http4s:http4s-ember-core_2.12 <= 0.23.34`
- `org.http4s:http4s-ember-core_2.13 <= 0.23.34`
- `org.http4s:http4s-ember-core_3 <= 0.23.34`
- `org.http4s:http4s-ember-core_3 >= 1.0.0-M1, <= 1.0.0-M46`
- `org.http4s:http4s-ember-core_2.13 >= 1.0.0-M1, <= 1.0.0-M46`

Patched in:

- `org.http4s:http4s-ember-core_2.12 0.23.35`
- `org.http4s:http4s-ember-core_2.13 0.23.35`
- `org.http4s:http4s-ember-core_3 0.23.35`
- `org.http4s:http4s-ember-core_3 1.0.0-M47`
- `org.http4s:http4s-ember-core_2.13 1.0.0-M47`

Source: https://github.com/advisories/GHSA-8f3q-3jmv-7prw