minimatch has a ReDoS via repeated wildcards with non-matching literal in pattern

Summary

minimatch is vulnerable to Regular Expression Denial of Service (ReDoS) when a glob pattern contains many consecutive * wildcards followed by a literal character that doesn't appear in the test string. Each * compiles to a separate [^/]*? regex group, and when the match fails, V8's regex engine backtracks exponentially across all possible splits.

The time complexity is O(4^N) where N is the number of * characters. With N=15, a single minimatch() call takes ~2 seconds. With N=34, it hangs effectively forever.

Details

Give all details on the vulnerability. Pointing to the incriminated source code is very helpful for the maintainer.

PoC

When minimatch compiles a glob pattern, each * becomes [^/]*? in the generated regex. For a pattern like ***************X***:

/^(?!\.)[^/]*?[^/]*?[^/]*?[^/]*?[^/]*?[^/]*?[^/]*?[^/]*?[^/]*?[^/]*?[^/]*?[^/]*?[^/]*?[^/]*?[^/]*?X[^/]*?[^/]*?[^/]*?$/

When the test string doesn't contain X, the regex engine must try every possible way to distribute the characters across all the [^/]*? groups before concluding no match exists. With N groups and M characters, this is O(C(N+M, N)) — exponential.

Impact

Any application that passes user-controlled strings to minimatch() as the pattern argument is vulnerable to DoS. This includes:

• File search/filter UIs that accept glob patterns
• .gitignore-style filtering with user-defined rules
• Build tools that accept glob configuration
• Any API that exposes glob matching to untrusted input

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Thanks to @ljharb for back-porting the fix to legacy versions of minimatch.