CVE-2026-69209 Details
Description
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, The shared WebSocket decoder permits unbounded message buffering because defragmentation accumulates fragments without a limit and FrameTranscoder accepts declared lengths up to Int.MaxValue. A remote client that completes a WebSocket handshake against an http4s-blaze-server or http4s-ember-server endpoint can exhaust server memory with oversized frames or fragmented messages. The patched decoder applies a configurable 64 MiB default limit to individual frames and defragmented messages through EmberServerBuilder.withMaxWebSocketMessageSize. This issue is fixed in versions 0.23.35 and 1.0.0-M47.
A denial-of-service vulnerability has been identified in http4s, a Scala library for HTTP services, specifically in versions prior to 0.23.35 and 1.0.0-M47. The issue arises in the WebSocket decoder, which allows unbounded message buffering. This occurs because the defragmentation process accumulates fragments without limit, and the FrameTranscoder accepts declared lengths up to Int.MaxValue. As a result, a remote client can exhaust server memory by sending oversized frames or fragmented messages. This vulnerability is present in the core WebSocket model shared by http4s-blaze-server and http4s-ember-server.
Users can upgrade to http4s versions 0.23.35 or 1.0.0-M47, where this vulnerability has been fixed. After upgrading, the WebSocket message size limit can be configured using 'EmberServerBuilder.withMaxWebSocketMessageSize'.
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 16, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/http4s/http4s/commit/d578c3c9da6193627d40fa785e612cda7fcd77b3 | [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-jrxx-w2m8-5hf5 | [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 16, 2026 | CVE Modified | CISA-ADP |
| Sep 15, 2026 | New CVE Received | [email protected] |