CVE-2026-11564: Haxx Curl

Critical severity, CVSS 9.1. EPSS: 0.4% chance of exploitation in the next 30 days.

libcurl keeps previously used connections in a connection pool for subsequent transfers to reuse if one of them matches the setup. An easy handle that first uses default native CA trust can continue trusting the native platform store after the application switches that same handle to custom CA material for a later transfer.

Affected products

• Haxx Curl: from 8.17.0, before 8.21.0 (fixed in 8.21.0)

Published 2026-07-03. Last modified 2026-09-15.