Path-to-Regexp is a small, yet powerful, utility for converting Express-style route paths into regular expressions, ideal for routing logic in web applications, servers, and more. Examining versions 0.2.4 and 0.2.5 reveals subtle but significant updates for developers seeking precise route matching. Both versions share the same core functionality, description, development dependencies (mocha for testing and istanbul for code coverage), MIT license, and repository. The crucial difference lies in the release date, with version 0.2.5 released on August 7, 2014, subsequent to version 0.2.4 released on August 2, 2014. This temporal gap suggests that version 0.2.5 likely incorporates bug fixes, performance improvements, or minor enhancements not found in its predecessor. For developers, upgrading to version 0.2.5 is recommended to benefit from the latest refinements and ensure optimal performance. The dist.tarball URLs point to where each version can be downloaded from the npm registry. By leveraging Path-to-Regexp, developers can efficiently define routes with parameters, optional segments, and regular expression matching, adding flexibility to their routing implementations. Keep up to date with the latest releases to make sure you get the best experience.
All the vulnerabilities related to the version 0.2.5 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.
