CVE-2026-69210 Http4s - Denial of Service

Http4s < 0.23.35 and < 1.0.0-M47 contain a denial of service caused by improper handling of negative 64-bit WebSocket frame lengths in FrameTranscoder.bodyLength, letting remote clients cause infinite decode loops and resource exhaustion, exploit requires completing a WebSocket handshake through Ember server.

CVSS base score 7.5 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.63% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Denial of Service
Impact
Denial Of Service
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
15 September 2026
Updated
15 October 2026
Weakness
CWE-835

Vendor fix

Upgrade to versions 0.23.35 or 1.0.0-M47 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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