CVE-2026-59724
High
Description
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.
SeverityHigh
CVSS7.5
Exploit probability—
ProductSocket Engine.io
PublishedJul 8, 2026
First seenJul 8, 2026
Weakness typeCWE-20Improper input validation
How to fix
Update
- socket engine.io6.6.7 or later
- engine.io6.6.7 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| socket engine.io | 6.5.0 ≤ v < 6.6.7 | 6.6.7 |
| engine.ionpm | 6.5.0 ≤ v < 6.6.7 | 6.6.7 |
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