GHSA-f38f-5xpm-9r7c: CairoSVG vulnerable to Exponential DoS via recursive <use> element amplification

CairoSVG (an SVG image processing library) has a denial-of-service vulnerability where recursive `<use>` elements (SVG tags that reference other graphics elements) can be nested without limits, causing exponential CPU exhaustion. A tiny 1,411-byte SVG file with just 5 levels of nesting and 10 references each triggers 100,000 render calls, pinning CPU at 100% indefinitely.