Path-to-regexp v1.0.2 refines v1.0.1, offering developers a subtle but potentially important update to this popular Express-style path-to-RegExp utility. Both versions cater to the core need of converting route paths into regular expressions, making them invaluable for routing and URL matching in web applications and APIs. Key differences highlight a refinement of the project's infrastructure and dependency management. Version 1.0.2 introduces a declared dependency with "isarray": "0.0.1" which was not present in the previous version. The update indicates a potentially strengthened reliance on robust array handling, possibly addressing edge cases and contributing to more reliable route parsing. More significantly, the repository URL in the package metadata changes from github.com/component/path-to-regexp.git in v1.0.1 to github.com/pillarjs/path-to-regexp.git in v1.0.2. This signals a change in project ownership or management, likely reflecting a move to a new maintainer or organization. Developers should check the new repository for issue tracking, contribution guidelines, and updated documentation. While the core functionality remains the same, these changes signify more than a simple patch. They suggest a potentially more active development and maintenance cycle under the new ownership, which benefits developers long-term. Upgrading from v1.0.1 to v1.0.2 is generally recommended to stay aligned with potential future improvements and ensure compatibility with the evolving ecosystem.
All the vulnerabilities related to the version 1.0.2 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.
