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.
Advisories
Source ID Title
Github GHSA Github GHSA GHSA-pq4g-8rxf-4g29 Crass: Incorrect tokenization of bad URLs enables CSS sanitizer bypass
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Wed, 28 Oct 2026 22:15:00 +0000

Type Values Removed Values Added
First Time appeared Rgrove
Rgrove crass
Vendors & Products Rgrove
Rgrove crass

Tue, 27 Oct 2026 20:30:00 +0000

Type Values Removed Values Added
Description 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.
Title Crass: Incorrect tokenization of bad URLs enables CSS sanitizer bypass
Weaknesses CWE-436
References
Metrics cvssV4_0

{'score': 5.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-10-27T20:10:34.010Z

Reserved: 2026-10-26T20:00:59.831Z

Link: CVE-2026-116695

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Deferred

Published: 2026-10-27T21:18:05.473

Modified: 2026-10-28T15:24:56.033

Link: CVE-2026-116695

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-28T21:48:00Z

Weaknesses