Grav before 2.0.4 contains a regular expression denial of service (ReDoS) vulnerability in the regex_replace filter and function, which are allowlisted in the Twig content sandbox. When Twig processing in page content is enabled (security.twig_content.process_enabled: true, disabled by default), an authenticated page editor can supply a catastrophically backtracking PCRE pattern that is passed directly to PHP's preg_replace(), causing unbounded CPU consumption and denial of service to the web server process.
Exploitability
AV:NAC:LAT:PPR:LUI:NVulnerable System
VC:NVI:NVA:HSubsequent System
SC:NSI:NSA:N6/CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:NResource Management