CVE-2026-69203
Http4s Ember HTTP/2: does not enforce SETTINGS_MAX_CONCURRENT_STREAMS
CVSS Score
7.5
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-400 CWE-770 |
| Vendor | http4s |
| Product | http4s |
| Published | Sep 15, 2026 |
| Last Updated | Sep 15, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Affected Versions
http4s / http4s
< 0.23.35 >= 1.0.0-M1, < 1.0.0-M47
References
github.com: 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: https://github.com/http4s/http4s/releases/tag/v1.0.0-M47