CVE-2026-102599: high-severity vulnerability in socketio socket.io
Socket.IO: Engine.IO Protocol Revision Mismatch DoS
Published · Updated
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.5epss 0.6%
Socket.IO enables bidirectional and low-latency communication for every platform. From Engine.IO 6.6.0 until 6.6.10, a transport upgrade can independently derive an Engine.IO protocol revision from the upgrade request instead of enforcing the revision stored on the existing session. A malicious client can establish a valid session and send an upgrade request with a different or omitted EIO query parameter, attaching a transport with incompatible parser and heartbeat behavior. A crafted heartbeat packet can then trigger an uncaught exception and terminate the Node.js process, including when Engine.IO v3 compatibility is disabled because an omitted EIO value is interpreted as revision 3 on the affected path. This issue is fixed in Engine.IO 6.6.10.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected products
socketio · socket.ioRelated CVEs — socketio socket.io
In the same product, most dangerous first.
CVE-2024-38355HIGHUnhandled 'error' event in socket.ioEPSS 0.8%CVE-2026-69185HIGHSocket.IO: Zero-attachment Memory ExhaustionEPSS 0.6%CVE-2026-59724HIGHSocket.IO: Engine.IO WebTransport SID DoSEPSS 0.6%CVE-2026-33151HIGHsocket.io allows an unbounded number of binary attachmentsEPSS 0.5%CVE-2026-102600HIGHSocket.IO: Prototype Pollution via Unsafe Client Session LookupEPSS 0.4%