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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.
Base Score
5.8| Package (Ecosystem) | Introduced | Fixed | Limit |
|---|---|---|---|
| css_parser(RubyGems) | 2.0.0 | 2.1.0 | N/A |
| css_parser(RubyGems) | 0 | 1.22.0 | N/A |
| Base Score | 5.8 |
|---|---|
| Vector String | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N |
| Base Severity | Medium |
| Version | 3.1 |
| Attack Vector (AV) | NETWORK |
