Vulnerability details

CVE-2026-69203

http4s http4s

Http4s Ember HTTP/2: does not enforce SETTINGS_MAX_CONCURRENT_STREAMS

CVSS 3.1

7.5High

Official 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.

CVSS scores

Score	Version	Source	Vector
7.5High	3.1	CVEProject cvelistV5 (CNA) (GitHub_M)	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`

Affected products

Vendor	Product	Versions	Source
http4s	http4s	< 0.23.35	CVEProject cvelistV5 (CNA)
http4s	http4s	>= 1.0.0-M1, < 1.0.0-M47	CVEProject cvelistV5 (CNA)

References and advisories

https://github.com/http4s/http4s/security/advisories/GHSA-9vwc-pc8p-253q x_refsource_CONFIRM
https://github.com/http4s/http4s/commit/4983de1f93f2caaa3b9de310cf6a9db32c50d66e x_refsource_MISC
https://github.com/http4s/http4s/releases/tag/v0.23.35 x_refsource_MISC
https://github.com/http4s/http4s/releases/tag/v1.0.0-M47 x_refsource_MISC

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Details

Published: 2026-09-15
Last updated: 2026-09-15
State: Published
Assigner (CNA): GitHub_M

Exploit prediction (EPSS)

0.63%

Probability of exploitation in 30 days

50.4%

Percentile (among all CVEs)

SSVC assessment (CISA)

Automatable: Yes
Exploitation: None
Technical impact: Partial

Weaknesses (CWE)

CWE-400
Uncontrolled Resource Consumption
CWE-770
Allocation of Resources Without Limits or Throttling