CVE-2026-4873: Haxx Curl

Medium severity, CVSS 5.9. EPSS: 0.4% chance of exploitation in the next 30 days.

A vulnerability exists where a connection requiring TLS incorrectly reuses an existing unencrypted connection from the same connection pool. If an initial transfer is made in clear-text (via IMAP, SMTP, or POP3), a subsequent request to that same host bypasses the TLS requirement and instead transmit data unencrypted.

Affected products

• Haxx Curl: from 7.20.0, before 8.20.0 (fixed in 8.20.0)

Published 2026-05-13. Last modified 2026-09-15.