Vulnerability in Socket Engine.io
CVE-2026-59725
Socket.IO enables bidirectional and low-latency communication for every platform. From 4.1.0 before 6.6.7, Engine.IO protocol v4 polling transport does not properly close the HTTP response for invalid binary POST requests with Content-Type: application/octet-stream, allowing an unauthenticated attacker to exhaust server-side connections and sockets. This issue is fixed in version 6.6.7.
EPSS: 0.004 (28.7th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
Affected products
- Socket Engine.io
- Socketio Socket.io — versions >= 4.1.0, < 6.6.7
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Patch, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-59725?
- CVE-2026-59725 is a high-severity vulnerability in Socket Engine.io, classified under Improper Resource Shutdown or Release. CVSS score: 7.5/10. Published 2026-07-08.
- How severe is CVE-2026-59725?
- High severity. CVSS v3 base score is 7.5 out of 10.