CVE-2026-80255: Haxx Curl

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

A `Set-Cookie:` header using tab (horizontal tab, ASCII code 9) instead of space (ascii code 32) immediately before the `Secure` attribute causes curl to store the cookie without its Secure flag. The cookie might then wrongfully be sent over plaintext HTTP on subsequent requests to the same host.

Affected products

• Haxx Curl: from 8.13.0, before 8.22.0 (fixed in 8.22.0)

Published 2026-09-06. Last modified 2026-09-15.