rails-html-sanitizer is responsible for sanitizing HTML fragments in Rails applications. From 1.0.3 through 1.7.1, Rails::HTML::PermitScrubber checks SVG href and xlink:href local references with a pattern whose line-start anchor and whitespace class cause an all-whitespace value to be rescanned from each line start. An attacker who supplies HTML can cause quadratic CPU consumption when an application customizes its allowed tags to include an SVG reference element such as use and permits href or xlink:href. The default allowed tag configuration is not affected. CRuby 3.2 and later uses linear-time regular expression matching for this pattern, while CRuby 3.1 and earlier and JRuby are affected. This issue is fixed in version 1.7.2.