Crass: A large number of adjacent CSS comments can trigger a SystemStackError

published 2026-10-29 10 d ago modified 2026-10-30 9 d ago also GHSA-wwpr-jff3-395c , EUVD-2026-114323

cvss: 6.3; version 4.0, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits: 0; none known

Crass is a Ruby CSS parser that's fully compliant with the CSS Syntax Level 3 specification. Prior to 1.0.7, when the `:preserve_comments` option is not enabled, which is the default, Crass discards CSS comments by recursively consuming the next token. An attacker-provided stylesheet containing a very large number of adjacent comments can cause excessive recursion and trigger a `SystemStackError`, denying service to the parsing application. Preserving comments avoids this recursive path. This issue is fixed in version 1.0.7.

Patch / fix

fixed in 1 distros 1 links 2

rubygems crass 1.0.7

ruby-crass Debian 14 1.0.7-1

debian advisories DEBIAN-CVE-2026-61847

github.com/rgrove/crass@25d78cc commit
github.com/rgrove/crass/releases/tag/v1.0.7 release

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-61847 updated 2026-11-04 cvss 7.5

crass: crass: Denial of Service via excessive recursion when processing comments

Red Hat 3scale API Management Platform 2 3scale-amp2/zync-rhel9, 3scale-amp2/system-rhel8
affected: no fix planned “Will not fix”
Red Hat Satellite 6 rubygem-crass 1.0.6-2.el9sat
affected: no fix available
Red Hat 3scale API Management Platform 2 3scale-amp2/system-rhel9
not affected: vulnerable code cannot be controlled by adversary

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 9 d ago (2026-10-30)

Exploit prediction

0.49% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	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
CNA	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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem	package	affected	fixed in
rubygems	crass	<1.0.7	1.0.7

Affected products

rgrove crass

Classification

Weakness

CWE-674 Uncontrolled Recursion

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary