# CVE-2026-61846: Crass: Deeply nested CSS blocks and functions can trigger a SystemStackError or excessive memory usage

Status: published. Published: 2026-10-30. Updated: 2026-11-05.

Crass is a Ruby CSS parser that's fully compliant with the CSS Syntax Level 3 specification. Prior to 1.0.7, Crass recursively parses `CSS simple blocks and functions` without a depth guard. An attacker-controlled CSS value containing deeply nested blocks or functions can recurse until Ruby raises `SystemStackError`: stack level too deep, or cause excessive memory usage. Version 1.0.7 adds a configurable depth limit with a conservative default. This issue is fixed in version 1.0.7.

## Remediation

- fix: crass (RubyGems): OSV reports a fixed version 1.0.7. Check the advisory for supported release branches. (source: OSV GHSA-6jxj-px6v-747w) — https://github.com/advisories/GHSA-6jxj-px6v-747w

## Affected products and versions

- rgrove / crass: < 1.0.7 (affected). Source: CNA: GitHub_M
-  / crass (crass): 0.0.1 (affected, RubyGems); 0.0.2 (affected, RubyGems); 0.1.0 (affected, RubyGems); 0.2.0 (affected, RubyGems); 0.2.1 (affected, RubyGems); 1.0.0 (affected, RubyGems); 1.0.1 (affected, RubyGems); 1.0.2 (affected, RubyGems); 1.0.3 (affected, RubyGems); 1.0.4 (affected, RubyGems); 1.0.5 (affected, RubyGems); 1.0.6 (affected, RubyGems); Ecosystem version events: introduced 0; fixed 1.0.7. Source: OSV GHSA-6jxj-px6v-747w

## Severity and prioritization

- CVSS 4.0: 6.3 (medium); CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: 0.49% as of 2026-11-04; percentile 41.94%

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-674

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/rgrove/crass/security/advisories/GHSA-6jxj-px6v-747w (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/rgrove/crass/commit/cf68287356ec6e20d51cfc4a2d0c3912b7334e99 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/rgrove/crass/releases/tag/v1.0.7 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/advisories/GHSA-6jxj-px6v-747w (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-6jxj-px6v-747w (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-61846; retrieved 2026-11-05; source updated 2026-11-05

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-6jxj-px6v-747w; retrieved 2026-11-05; source updated 2026-10-29

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-61846; retrieved 2026-11-05; source updated Not reported

Revision: b62d85c9454bfa739fc6ff649b8a8562bc3f9ce0d5b3ff465100657a6666ce13

Canonical: https://y2.dev/cve/CVE-2026-61846

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