---
id: CVE-2026-69203
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,
  An Ember server with HTTP/2 enabled through withHttp2 does not enforce
  SETTINGS_MAX_CONCURRENT_STREAMS for peer-created streams. One unauthenticated
  connectio…
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: 'org.http4s:http4s-ember-core_2.12'
affected:
  - '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_2.13 >= 1.0.0-M1, <= 1.0.0-M46'
  - 'org.http4s:http4s-ember-core_3 >= 1.0.0-M1, <= 1.0.0-M46'
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_2.13 1.0.0-M47'
  - 'org.http4s:http4s-ember-core_3 1.0.0-M47'
published: '2026-09-15'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T20:38:04.943'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-69203'
references:
  - url: >-
      https://github.com/http4s/http4s/commit/4983de1f93f2caaa3b9de310cf6a9db32c50d66e
    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-9vwc-pc8p-253q'
    label: security-advisories@github.com
  - url: 'https://github.com/advisories/GHSA-9vwc-pc8p-253q'
tags:
  - nvd
  - ghsa
  - maven
  - cve.org
aliases:
  - GHSA-9vwc-pc8p-253q
ecosystem: maven
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-15T19:36:24.682974Z'
ingestedAt: '2026-09-15T19:42:58.814Z'
epss: 0.0046
epssPercentile: 0.39189
---

## Overview

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, An Ember server with HTTP/2 enabled through withHttp2 does not enforce SETTINGS_MAX_CONCURRENT_STREAMS for peer-created streams. One unauthenticated connection can open an unbounded number of streams, each retaining per-stream state until heap exhaustion. The same unchecked allocation is reachable in an ember-client through server-initiated PUSH_PROMISE frames because enablePush is not enforced. 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-2026-69203)

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_2.13 >= 1.0.0-M1, <= 1.0.0-M46`
- `org.http4s:http4s-ember-core_3 >= 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_2.13 1.0.0-M47`
- `org.http4s:http4s-ember-core_3 1.0.0-M47`

Source: https://github.com/advisories/GHSA-9vwc-pc8p-253q