CVE-2018-20821: The parsing component in LibSass through 3.5.5 allows attackers to cause a denial-of-service (uncontrolled...

Security readout for executives and security teams

CVE-2018-20821 is a denial-of-service flaw in LibSass through 3.5.5. A specially crafted Sass/CSS input can trigger uncontrolled recursion in the parser, potentially crashing or exhausting resources in systems that process untrusted stylesheet content. Exposure is most likely in build pipelines, web tooling, CMS features, or services that invoke LibSass on attacker-controlled Sass/CSS input. Systems only compiling trusted local stylesheets have lower practical exposure. Treat this as a targeted availability risk, not a broad remote code execution emergency based on available evidence. Prioritize internet-facing or customer-controlled stylesheet processing paths first. Mitigation focus: Identify LibSass use and version across applications and build tooling.; Check vendor or distribution guidance for fixed LibSass packages.; Prioritize systems parsing user-submitted stylesheet content..

Prepared

Jun 6, 2026, 21:12 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.