CVE-2026-69203 Details
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.
A denial-of-service vulnerability has been identified in Http4s versions prior to 0.23.35 and 1.0.0-M47. The issue arises in the Ember server when HTTP/2 is enabled. The server fails to enforce the maximum number of concurrent streams allowed, allowing a single unauthenticated connection to open an unlimited number of streams. Each stream consumes server resources that are not released, leading to memory exhaustion. This vulnerability can also be exploited in the Ember client through server-initiated PUSH_PROMISE frames, causing similar heap exhaustion.
Users can upgrade to Http4s versions 0.23.35 or 1.0.0-M47, where this vulnerability has been patched. Instructions for upgrading can be found in the release notes on the Http4s GitHub repository.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Sep 15, 2026CISA-ADP
Assessed Sep 15, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/http4s/http4s/commit/4983de1f93f2caaa3b9de310cf6a9db32c50d66e | [email protected] | Source CodeVendor |
| https://github.com/http4s/http4s/releases/tag/v0.23.35 | [email protected] | Release NotesVendor |
| https://github.com/http4s/http4s/releases/tag/v1.0.0-M47 | [email protected] | Release NotesVendor |
| https://github.com/http4s/http4s/security/advisories/GHSA-9vwc-pc8p-253q | [email protected] | AdvisoryRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-400 | Uncontrolled Resource Consumption | [email protected] |
| CWE-770 | Allocation of Resources Without Limits or Throttling | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| http4s | <= 0.23.34 (semver) >= 1.0.0-M1, <= 1.0.0-M46 (semver) |
CPE
Remediation
| |
| http4s-ember-core | <= 0.23.34 (semver) >= 1.0.0-M1, <= 1.0.0-M46 (semver) |
CPE
Remediation
| |
Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 15, 2026 | New CVE Received | [email protected] |
| Sep 15, 2026 | CVE Modified | CISA-ADP |