Path-to-Regexp is a utility that converts Express-style route paths into regular expressions, simplifying route matching in JavaScript applications. Comparing versions 1.6.0 and 1.7.0 highlights a minor release with a few subtle changes, but ultimately retaining the core functionality that makes it valuable for developers..
Both versions maintain identical dependencies, relying solely on "isarray" version 0.0.1. The development dependencies, crucial for testing and code quality are the similar, including tools like Chai for assertions, Mocha for testing framework, ts-node & typescript for typescript transpilation, and Istanbul for code coverage, suggesting a consistent development and testing process. The consistent MIT license assures developers of its free and open-source nature. The repository URL remains the same, also confirming the library's home.
Examining the release dates shows that version 1.7.0 was released on November 8, 2016, approximately a month after version 1.6.0, released on October 3, 2016. The primary difference lies in the likely bug fixes, minor improvements, or optimizations implemented in version 1.7.0. Given the absence of major version number change, breaking changes are improbable.
For developers, Path-to-Regexp offers a simple way to define routes using familiar Express-like syntax, and then transform those routes into regular expressions suitable for matching against incoming paths, this enables building routing logic for various web applications and frameworks. The minor update indicates continued maintenance and refinement. Upgrading from 1.6.0 to 1.7.0 should be seamless.
All the vulnerabilities related to the version 1.7.0 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.
