KITFORMA · EDITORIAL GUIDE
Why can a short-looking regex take seconds on an invalid long string?
KitForma editorial guide. Nested or ambiguous repetition can make a backtracking regex explore many possible matches before rejecting input. Pattern length alone does not predict runtime.
Step-by-step guidance
Nested or ambiguous repetition can make a backtracking regex explore many possible matches before rejecting input. Pattern length alone does not predict runtime.
Simplify overlapping alternatives, anchor where the contract requires a full string, and cap input length before matching. Test long near-matches that fail at the final character, not only successful examples. Where appropriate, use a parser or a regex engine with suitable complexity guarantees. Python standard
re does not provide a general per-match timeout argument. Running a vulnerable pattern on a public endpoint without bounds can monopolize a worker even if all normal unit tests are fast.Sources and verification
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