Path-to-regexp version 7.1.0 represents a recent update to this popular utility that translates Express-style path strings into regular expressions. Comparing it to the prior stable version 7.0.0, a key difference lies in the introduction of the "recheck" dev dependency, alongside an updated TypeScript dependency (now at ^5.5.3, previously ^5.1.6), suggesting improvements in code quality, security, and developer experience, likely from static analysis and enhanced type safety. The slightly increased unpacked size (64954 bytes vs 59789 bytes) possibly signals new features, refined algorithms, or expanded test coverage. Both versions maintain the MIT license, offering flexibility in usage. The unchanged URL repository confirms updates within the same established project. For developers, path-to-regexp facilitates routing and URL matching in applications, essential for building web servers, single-page applications, and APIs. The update offers potentially better performance and aligns the project with the latest TypeScript features, ensuring compatibility and maintainability. Developers should evaluate the change log for 7.1.0 for precise details on incorporated bug fixes or enhancements. The releaseDate difference points to a recent effort in continuous improvement, making it a viable choice for projects seeking current, robust path handling.
All the vulnerabilities related to the version 7.1.0 of the package
path-to-regexp outputs backtracking regular expressions
A bad regular expression is generated any time you have two parameters within a single segment, separated by something that is not a period (.). For example, /:a-:b.
For users of 0.1, upgrade to 0.1.10. All other users should upgrade to 8.0.0.
These versions add backtrack protection when a custom regex pattern is not provided:
They do not protect against vulnerable user supplied capture groups. Protecting against explicit user patterns is out of scope for old versions and not considered a vulnerability.
Version 7.1.0 can enable strict: true and get an error when the regular expression might be bad.
Version 8.0.0 removes the features that can cause a ReDoS.
All versions can be patched by providing a custom regular expression for parameters after the first in a single segment. As long as the custom regular expression does not match the text before the parameter, you will be safe. For example, change /:a-:b to /:a-:b([^-/]+).
If paths cannot be rewritten and versions cannot be upgraded, another alternative is to limit the URL length. For example, halving the attack string improves performance by 4x faster.
Using /:a-:b will produce the regular expression /^\/([^\/]+?)-([^\/]+?)\/?$/. This can be exploited by a path such as /a${'-a'.repeat(8_000)}/a. OWASP has a good example of why this occurs, but the TL;DR is the /a at the end ensures this route would never match but due to naive backtracking it will still attempt every combination of the :a-:b on the repeated 8,000 -a.
Because JavaScript is single threaded and regex matching runs on the main thread, poor performance will block the event loop and can lead to a DoS. In local benchmarks, exploiting the unsafe regex will result in performance that is over 1000x worse than the safe regex. In a more realistic environment using Express v4 and 10 concurrent connections, this translated to average latency of ~600ms vs 1ms.
