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.

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Source ID Title
Github GHSA Github GHSA GHSA-9vwc-pc8p-253q Http4s Ember HTTP/2 does not enforce SETTINGS_MAX_CONCURRENT_STREAMS
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Tue, 15 Sep 2026 21:45:00 +0000

Type Values Removed Values Added
First Time appeared Http4s
Http4s http4s
Vendors & Products Http4s
Http4s http4s

Tue, 15 Sep 2026 20:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 15 Sep 2026 19:30:00 +0000

Type Values Removed Values Added
Description 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.
Title Http4s Ember HTTP/2: does not enforce SETTINGS_MAX_CONCURRENT_STREAMS
Weaknesses CWE-400
CWE-770
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-15T19:36:32.272Z

Reserved: 2026-08-03T16:57:50.124Z

Link: CVE-2026-69203

cve-icon Vulnrichment

Updated: 2026-09-15T19:36:29.213Z

cve-icon NVD

Status : Received

Published: 2026-09-15T20:17:39.120

Modified: 2026-09-15T20:17:39.120

Link: CVE-2026-69203

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-15T21:30:15Z

Weaknesses