---
id: CVE-2026-88975
title: Http4s is a Scala interface for HTTP services
summary: >-
  Http4s is a Scala interface for HTTP services. Prior to 0.23.37 and 1.0.0-M48,
  Ember’s HTTP/2 read loop parses a frame’s 24-bit declared length but waits to
  buffer the entire payload before comparing it with SETTINGS_MAX_FRAME_SIZE. An
  u…
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
vendor: http4s
product: http4s
affected:
  - http4s < 0.23.37
  - 'http4s >= 1.0.0-M1, < 1.0.0-M48'
patched:
  - 'org.http4s:http4s-ember-core_2.13 0.23.37'
  - 'org.http4s:http4s-ember-core_2.12 0.23.37'
  - 'org.http4s:http4s-ember-core_3 0.23.37'
  - 'org.http4s:http4s-ember-core_2.13 1.0.0-M48'
  - 'org.http4s:http4s-ember-core_3 1.0.0-M48'
published: '2026-09-15'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T20:39:16.610'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-88975'
references:
  - url: >-
      https://github.com/http4s/http4s/commit/87cf334fa3f608ef7d3eb359e71e037ba3336d29
    label: security-advisories@github.com
  - url: 'https://github.com/http4s/http4s/releases/tag/v0.23.37'
    label: security-advisories@github.com
  - url: 'https://github.com/http4s/http4s/releases/tag/v1.0.0-M48'
    label: security-advisories@github.com
  - url: 'https://github.com/http4s/http4s/security/advisories/GHSA-gq9p-f254-h286'
    label: security-advisories@github.com
  - url: 'https://github.com/advisories/GHSA-gq9p-f254-h286'
tags:
  - nvd
  - cve.org
  - ghsa
  - maven
aliases:
  - GHSA-gq9p-f254-h286
ecosystem: maven
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-16T14:43:06.919100Z'
ingestedAt: '2026-09-15T19:42:58.816Z'
epss: 0.00622
epssPercentile: 0.4847
---

## Overview

Http4s is a Scala interface for HTTP services. Prior to 0.23.37 and 1.0.0-M48, Ember’s HTTP/2 read loop parses a frame’s 24-bit declared length but waits to buffer the entire payload before comparing it with SETTINGS_MAX_FRAME_SIZE. An unauthenticated peer can declare a payload near 16 MiB on a connection where Ember advertised 16 KiB and either complete or slowly stream it, causing up to 1024-fold memory amplification per connection before processFrame can reject the frame. The shared H2Connection.readLoop affects withHttp2 servers and clients, while HTTP/2-disabled configurations are unaffected, and the patch rejects oversized frames before buffering their payloads. This issue is fixed in versions 0.23.37 and 1.0.0-M48.

## Remediation

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

## Package advisory (CVE-2026-88975)

Affected packages:

- `org.http4s:http4s-ember-core_2.13 <= 0.23.36`
- `org.http4s:http4s-ember-core_2.12 <= 0.23.36`
- `org.http4s:http4s-ember-core_3 <= 0.23.36`
- `org.http4s:http4s-ember-core_2.13 >= 1.0.0-M1, <= 1.0.0-M47`
- `org.http4s:http4s-ember-core_3 >= 1.0.0-M1, <= 1.0.0-M47`

Patched in:

- `org.http4s:http4s-ember-core_2.13 0.23.37`
- `org.http4s:http4s-ember-core_2.12 0.23.37`
- `org.http4s:http4s-ember-core_3 0.23.37`
- `org.http4s:http4s-ember-core_2.13 1.0.0-M48`
- `org.http4s:http4s-ember-core_3 1.0.0-M48`

Source: https://github.com/advisories/GHSA-gq9p-f254-h286