CVE-2026-69210
Http4s: WebSocket decoder accepts negative length, causing infinite decode loop
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, 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.
| CWE | CWE-835 CWE-1284 |
| Vendor | http4s |
| Product | http4s |
| Published | Sep 15, 2026 |
Stay Ahead of the Next One
Get instant alerts for http4s http4s
Be the first to know when new high vulnerabilities affecting http4s http4s are published — delivered to Slack, Telegram or Discord.
Get Free Alerts →
Free · No credit card · 60 sec setup
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-3j86-pj9g-jchr github.com: https://github.com/http4s/http4s/commit/c7d3ef90dc2ed1cd464968ab1b34f2f1762ddae2 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