Fetch-mock, a popular library for mocking HTTP requests in JavaScript environments (including browsers and Node.js), has released version 9.8.0, building upon the solid foundation of its predecessor, version 9.7.0. While the core functionality of mocking fetch remains consistent, subtle improvements and bug fixes likely differentiate the two versions. Developers relying on precise control over request handling will benefit from these refinements.
A key consideration for developers is the "releaseDate". Version 9.8.0 came out after version 9.7.0, it is more recent and could contain security fixes, better performance given the same functionalities or new functionalities.
Examining the "dist" section revels that version 9.8.0 has a slightly bigger "unpackedSize" of 2819223 comparing to 2818001 of version 9.7.0, suggesting minor code additions or alterations, maybe due to bug fixes or small features add ons. The "fileCount" remains constant at 39, indicating similar overall project structure. To choose the right version, developers should consult the fetch-mock's changelog or release notes to understand the specifics of what changed between versions 9.7.0 and 9.8.0. Pay attention to bug fixes that may impact existing code or new features that could simplify mocking scenarios.
Both versions support a wide array of testing frameworks, evident from the "devDependencies" like Mocha, Chai, and Sinon, offering flexibility in test setup. The presence of tools like Rollup and Webpack suggests the library is optimized for various bundling strategies, providing ease of integration into modern JavaScript projects. The peer dependency on node-fetch in both versions highlights their adaptability to both browser and server-side environments.
All the vulnerabilities related to the version 9.8.0 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.
