CVE-2026-56866: HTTP/1 client connection desynchronization after CONNECT rejection in net/http

Overview

Severity

High (CVSS 7.5)

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Exploit Status

Not Exploited

Patch Tuesday

2026-Oct

Released

2026-10-11

Last Updated

2026-10-12

EPSS Score

0.31% (percentile: 21.9%)

Affected Products (2)

Other

• 19693-17084
• 21021-17084

Revision History

• 2026-10-11: Information published.
• 2026-10-12: Information published.