Crass: Deeply nested CSS blocks and functions can trigger a SystemStackError or excessive memory usage

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.3 · 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 · score source

EPSS

• CVE-2026-61846: 0.49% estimated exploitation activity in the next 30 days; percentile 41.86 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Crass recursively parses CSS simple blocks and functions without a depth guard. An attacker-controlled value containing many deeply nested blocks can recurse until Ruby raises `SystemStackError: stack level too deep`, or can cause excessive memory usage.

Patches This is fixed in Crass 1.0.7, which adds a configurable depth limit with a conservative default.

Workarounds Add `SystemStackError` handling around Crass calls in your application. Buy more RAM.

Published by the source

29 Oct 2026, 16:35 UTC

Last modified by the source

29 Oct 2026, 16:45 UTC

Source last checked

30 Oct 2026, 07:10 UTC

1. Revision 2 · amended · 30 Oct 2026

   Amended from osv record GHSA-6jxj-px6v-747w

2. Revision 1 · created · 29 Oct 2026

   Published from ghsa record GHSA-6jxj-px6v-747w

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# Patch Next advisory brief: CVE-2026-61846

Advisory: Crass: Deeply nested CSS blocks and functions can trigger a SystemStackError or excessive memory usage
IDs: CVE-2026-61846, GHSA-6jxj-px6v-747w
Record: https://patchnext.com/advisories/cve-2026-61846 (revision 2, source checked 30 Oct 2026, 07:10 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: crass 1.0.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems crass: affected < 1.0.7; fixed in 1.0.7

## Suggested inspection (read-only)
- RubyGems crass: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on crass.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-6jxj-px6v-747w (GitHub-reviewed advisory GHSA-6jxj-px6v-747w lists affected ranges: RubyGems crass >=0 <1.0.7)
- Verified: https://osv.dev/vulnerability/GHSA-6jxj-px6v-747w (OSV record GHSA-6jxj-px6v-747w lists affected ranges: RubyGems crass >=0 <1.0.7 (fixed))

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