Path-to-regexp is a utility that converts Express-style path strings into regular expressions, providing a flexible solution for route matching and parameter extraction in JavaScript applications, especially useful in frameworks and libraries dealing with routing. Comparing version 1.1.0 with the preceding stable version 1.0.3 reveals key improvements for developers. Both versions share the core functionality and the "isarray" dependency. However, version 1.1.0 introduces several significant updates to the development workflow and tooling.
Most notably, 1.1.0 integrates modern JavaScript style linting through "standard" and automates pre-commit tasks using "pre-commit," ensuring code quality and consistency. Chai has also been added, suggesting an improvement in the testing suite of the library. This indicates a stronger focus on code quality and maintainability. While both versions utilize Mocha for testing and Istanbul for code coverage reporting, 1.1.0 updates Mocha to a more recent version, suggesting potential improvements in test execution and reporting.
Developers upgrading to 1.1.0 will benefit from these improved development practices, resulting in a more robust and reliable library. Since they use the same core functionality this upgrade should not have breaking changes for the end user.
All the vulnerabilities related to the version 1.1.0 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.
