PatchSiren cyber security CVE debrief
CVE-2026-59725 socketio CVE debrief
CVE-2026-59725 is a high-severity vulnerability affecting Socket.IO's Engine.IO protocol. Versions from 4.1.0 to 6.6.6 are affected. The issue allows unauthenticated attackers to cause a denial of service by exhausting server-side connections and sockets through invalid binary POST requests with Content-Type: application/octet-stream. This vulnerability is fixed in version 6.6.7. The vulnerability has a CVSS score of 7.5 and is classified as HIGH severity. It is particularly concerning for applications relying on Socket.IO for real-time communication, as it can lead to denial-of-service attacks.
- Vendor
- socketio
- Product
- socket.io
- CVSS
- HIGH 7.5
- CISA KEV
- Not listed in stored evidence
- Original CVE published
- 2026-07-08
- Original CVE updated
- 2026-07-10
- Advisory published
- 2026-07-08
- Advisory updated
- 2026-07-10
Who should care
Developers and administrators using Socket.IO versions between 4.1.0 and 6.6.6 should prioritize upgrading to version 6.6.7 or later to mitigate this vulnerability. This issue is particularly concerning for applications relying on Socket.IO for real-time communication, as it can lead to denial-of-service attacks. Operators, platform administrators, vulnerability management teams, and security teams should review the affected scope and implement necessary mitigations.
Technical summary
The vulnerability in Socket.IO's Engine.IO protocol v4 polling transport does not properly close the HTTP response for invalid binary POST requests with Content-Type: application/octet-stream. This oversight allows an unauthenticated attacker to exhaust server-side connections and sockets, effectively causing a denial-of-service condition. The issue has a CVSS score of 7.5 and is classified as HIGH severity. The vulnerability is tracked under CWE-404.
Defensive priority
High
Recommended defensive actions
- Upgrade Socket.IO to version 6.6.7 or later
- Review and update affected applications relying on Socket.IO for real-time communication
- Monitor for unusual traffic patterns that could indicate exploitation attempts
- Implement additional security measures such as rate limiting for incoming requests
- Review compensating controls for exposed systems while remediation is scheduled and verified
- Check relevant monitoring, detection, and logs for exposed assets that need extra review
- Track exceptions, retest remediated assets, and close the item only after evidence is documented
Evidence notes
The CVE record was published on 2026-07-08T16:16:33.133Z and was last modified on 2026-07-10T19:01:16.053Z. The NVD entry is currently awaiting analysis. The vulnerability is tracked under CWE-404. Evidence is limited to CVE and NVD details. Defenders should verify affected versions and upgrade to 6.6.7 or later. Socket.IO's 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.
Official resources
AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-07-08T16:16:33.133Z and has not been modified since then.