Path-to-regexp versions 1.7.0 and 1.8.0 offer developers a utility for converting Express-style path strings into regular expressions, a crucial tool for routing and URL matching in web applications. Both versions share the same core functionality and dependencies, utilizing isarray for array checking and relying on the same suite of development tools including chai for assertions, mocha for testing, ts-node for TypeScript execution, typings for type definition management, istanbul for code coverage, standard for JavaScript style adherence, and typescript for development. The license remains consistent at MIT, offering developers freedom in usage and modification.
However, the key difference lies in their release dates and potentially internal improvements. Version 1.7.0 was released in November 2016, while version 1.8.0 came out in November 2019. This three-year gap suggests that version 1.8.0 might include bug fixes, performance enhancements, or minor feature additions not explicitly documented in the provided metadata. While the dependencies and devDependencies appear identical, internal code refinements may exist. Moreover, version 1.8.0 provides data about fileCount and unpackedSize. For developers considering upgrading, the newer version 1.8.0 is recommended due to the likelihood of stability and potential performance gains accumulated over those three years of development. Note that because of the identical configuration the effort of upgrade between the 2 versions is very likely to be minimal because no breaking change is expected.
All the vulnerabilities related to the version 1.8.0 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.
