GHSA-9wv6-86v2-598j

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GHSA-9wv6-86v2-598j

Summary: path-to-regexp outputs backtracking regular expressions

Details: ### Impact 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`. ### Patches 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: - [0.1.10](https://github.com/pillarjs/path-to-regexp/releases/tag/v0.1.10) - [1.9.0](https://github.com/pillarjs/path-to-regexp/releases/tag/v1.9.0) - [3.3.0](https://github.com/pillarjs/path-to-regexp/releases/tag/v3.3.0) - [6.3.0](https://github.com/pillarjs/path-to-regexp/releases/tag/v6.3.0) 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](https://github.com/pillarjs/path-to-regexp/releases/tag/v7.1.0) can enable `strict: true` and get an error when the regular expression might be bad. Version [8.0.0](https://github.com/pillarjs/path-to-regexp/releases/tag/v8.0.0) removes the features that can cause a ReDoS. ### Workarounds 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. ### Details Using `/:a-:b` will produce the regular expression `/^\/([^\/]+?)-([^\/]+?)\/?$/`. This can be exploited by a path such as `/a${'-a'.repeat(8_000)}/a`. [OWASP](https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS) 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. ### References * [OWASP](https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS) * [Detailed blog post](https://blakeembrey.com/posts/2024-09-web-redos/)

References: https://github.com/pillarjs/path-to-regexp/security/advisories/GHSA-9wv6-86v2-598j, https://nvd.nist.gov/vuln/detail/CVE-2024-45296, https://github.com/pillarjs/path-to-regexp/commit/29b96b4a1de52824e1ca0f49a701183cc4ed476f, https://github.com/pillarjs/path-to-regexp/commit/60f2121e9b66b7b622cc01080df0aabda9eedee6, https://github.com/pillarjs/path-to-regexp/commit/925ac8e3c5780b02f58cbd4e52f95da8ad2ac485, https://github.com/pillarjs/path-to-regexp/commit/d31670ae8f6e69cbfd56e835742195b7d10942ef, https://github.com/pillarjs/path-to-regexp/commit/f1253b47b347dcb909e3e80b0eb2649109e59894, https://github.com/pillarjs/path-to-regexp, https://github.com/pillarjs/path-to-regexp/releases/tag/v6.3.0, https://security.netapp.com/advisory/ntap-20250124-0001