CVE-2026-69210

Http4s: WebSocket decoder accepts negative length, causing infinite decode loop

State: Published
Severity: 7.5 High
Published: Sep 15, 2026
Updated: Sep 17, 2026
Reserved: Aug 3, 2026

Description

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, WebSocket FrameTranscoder.bodyLength rejects extended payload lengths above Integer.MAX_VALUE but permits negative 64-bit lengths. A remote client that completes a WebSocket handshake through an Ember server can send such a frame, causing the decoder to return an empty frame without advancing its input. The decode loop then runs indefinitely, pins a worker at full CPU, and grows an ArrayBuffer without bound, resulting in denial of service. This issue is fixed in versions 0.23.35 and 1.0.0-M47.

Scores

CVSS	Score	Vector	Source
3.1	7.5 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	GitHub_M

Weaknesses

CWE-835 Loop with Unreachable Exit Condition ('Infinite Loop')
CWE-1284 Improper Validation of Specified Quantity in Input

Affected Products

Product	Versions
http4shttp4s	< 0.23.35Affected >= 1.0.0-M1, < 1.0.0-M47Affected

References

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