CVE-2026-59724CWE-20

Socket.IO: Engine.IO WebTransport SID DoS

High · published July 8, 2026

CVSS v3.1
7.5
EPSS
1%
Percentile
48.5
In the wild
Unconfirmed
What it is

Socket.IO enables bidirectional and low-latency communication for every platform. From 6.5.0 before 6.6.7, Engine.IO servers with WebTransport enabled can resolve a crafted session ID such as __proto__ through an inherited property of the clients object during WebTransport upgrade handling, causing a TypeError and denial of service. This issue is fixed in version 6.6.7.

The record
Technical detail
CVSS v3.1
7.5 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS v4.0
Not supplied
EPSS
0.00609 · 48.5th percentile
Weakness
CWE-20 · Improper Input Validation
Published
2026-07-08T15:35Z
EPSS history
Timeline
  • 08 JUL 15:35Z
    Socket.IO: Engine.IO WebTransport SID DoS
    cvelistv5