CVE-2026-44312: Premailer Css Parser

Medium severity, CVSS 5.8. EPSS: 0.2% chance of exploitation in the next 30 days.

css_parser is a Ruby CSS parser. Prior to 2.1.0 and 1.22.0, the CSS Parser gem does not validate HTTPS connections, allowing a Man-in-the-Middle (MITM) attacker to inject or modify CSS content when stylesheets are loaded via HTTPS. The connection is established with OpenSSL::SSL::VERIFY_NONE, meaning any HTTPS certificate—even entirely untrusted—will be accepted without validation. This vulnerability is fixed in 2.1.0 and 1.22.0.

Affected products

• Premailer Css Parser: from 2.0.0, before 2.1.0 (fixed in 2.1.0); before 1.22.0 (fixed in 1.22.0)

Published 2026-05-14. Last modified 2026-06-17.