Crass is a Ruby CSS parser that is compliant with the CSS Syntax Level 3 specification. Prior to 1.0.8, Crass incorrectly treats a closing parenthesis after an escaped backslash as escaped while consuming the remnants of a bad URL. Crass therefore keeps declarations, style rules, or at-rules inside a bad URL token even though a browser treats them as live CSS. A sanitizer that parses untrusted CSS with Crass and reserializes it without rejecting the bad URL can allow CSS used for UI redress, external resource loading, or CSS-based data exfiltration, but this issue does not enable script execution in modern browsers. This issue is fixed in version 1.0.8.
Weakness
Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B’s state.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Ruby-crass | Ubuntu | upstream | * |
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/105.html
- https://cwe.mitre.org/data/definitions/273.html
- https://cwe.mitre.org/data/definitions/34.html