premailer css_parser up to 1.21.x/2.0.x inclusion of functionality from untrusted control sphere

Summaryinfo

A vulnerability described as problematic has been identified in premailer css_parser up to 1.21.x/2.0.x. This issue affects some unknown processing. Executing a manipulation can lead to inclusion of functionality from untrusted control sphere. This vulnerability appears as CVE-2026-44312. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability has been found in premailer css_parser up to 1.21.x/2.0.x and classified as problematic. This vulnerability affects an unknown code block. The manipulation with an unknown input leads to a inclusion of functionality from untrusted control sphere vulnerability. The CWE definition for the vulnerability is CWE-829. The product imports, requires, or includes executable functionality (such as a library) from a source that is outside of the intended control sphere. As an impact it is known to affect integrity. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-44312 since 05/05/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are neither technical details nor an exploit publicly available.

Upgrading to version 1.22.0 or 2.1.0 eliminates this vulnerability. Applying the patch 35e689c904225add78e0c488cf04bad052666449 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Vendor

• premailer

Name

• css_parser

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16
• 1.17
• 1.18
• 1.19
• 1.20
• 1.21
• 2.0

License

• open-source

Website

• Product: https://github.com/premailer/css_parser/

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