CVE-2026-8286: Haxx Curl

High severity, CVSS 8.1. EPSS: 0.3% chance of exploitation in the next 30 days.

A vulnerability exists where a new transfer that uses STARTTLS to upgrade the connection might reuse an existing live connection even though the TLS configuration mismatches so it should not.

Affected products

• Haxx Curl: from 7.30.0, before 8.21.0 (fixed in 8.21.0)

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