RE2JS: Quadratic-time denial of service in re2js lookbehind matching
Using the opt-in LOOKBEHINDS flag together with any repeated-matching API (matcher().find() in a loop, matchAll(), split(), matcher().replaceAll()) causes quadratic-time (Θ(n²)) matching, contradicting the library's own "linear time matching" guarantee. A single call with a 16,000-character input takes 36.7–38.7 seconds of CPU.