CVE-2026-69203

Http4s Ember HTTP/2: does not enforce SETTINGS_MAX_CONCURRENT_STREAMS

Published: Sep 15, 2026Updated: Sep 16, 2026 Sources: CVE List NVDCWE-400

7.5HIGH

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.

No summary for this CVE yet.

CVSS Vector Breakdown

Exploitability

AV:NAttack Vector

Network

AC:LAttack Complexity

Low

PR:NPrivileges Required

None

UI:NUser Interaction

None

Scope

S:UScope

Unchanged

Impact

C:NConfidentiality

None

I:NIntegrity

None

A:HAvailability

High

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Weaknesses

CWE-400 CWE-770

Affected Products

http4s

oss-projectaka blaze

http4sLibrary

OSS Libraries / web-framework

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

1 technique

Impact

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References

https://github.com/http4s/http4s/security/advisories/GHSA-9vwc-pc8p-253q

github.com

https://github.com/http4s/http4s/commit/4983de1f93f2caaa3b9de310cf6a9db32c50d66e

github.com

https://github.com/http4s/http4s/releases/tag/v0.23.35

github.com

and 1 more references View all →

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