Path-to-regexp version 7.2.0 represents a recent update to this widely used utility for converting Express-style path strings into regular expressions, a crucial tool for routing in web applications and APIs. Comparing it to the previous stable version, 7.1.0, several subtle but important changes emerge. Both versions share the same core development dependencies, including tools for testing, linting (recheck), size analysis (size-limit), TypeScript support, and associated type definitions, indicating a continued commitment to code quality and maintainability. The MIT license remains, ensuring broad compatibility for various projects.
One key difference lies in the unpacked size, with version 7.2.0 slightly larger at 65430 bytes compared to 7.1.0's 64954 bytes. While seemingly minor, this increase could reflect bug fixes, performance enhancements, or new features introduced in the latest version. The release date also highlights the significant advancement, with version 7.2.0 deployed in September 2024, indicating a more recent and potentially more refined codebase. Developers relying on path-to-regexp should consider upgrading to version 7.2.0 to benefit from the latest improvements and fixes. Before upgrading, it's recommended to review the changelog or release notes for a detailed breakdown of the changes and potential impact on existing applications. This ensures a smooth transition and optimal performance within your projects routing mechanisms.
All the vulnerabilities related to the version 7.2.0 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.
