GHSA-37ch-88jc-xwx2

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GHSA-37ch-88jc-xwx2

Summary: path-to-regexp vulnerable to Regular Expression Denial of Service via multiple route parameters

Details: ### Impact A bad regular expression is generated any time you have three or more parameters within a single segment, separated by something that is not a period (`.`). For example, `/:a-:b-:c` or `/:a-:b-:c-:d`. The backtrack protection added in `[email protected]` only prevents ambiguity for two parameters. With three or more, the generated lookahead does not block single separator characters, so capture groups overlap and cause catastrophic backtracking. ### Patches Upgrade to [[email protected]](https://github.com/pillarjs/path-to-regexp/releases/tag/v.0.1.13) Custom regex patterns in route definitions (e.g., `/:a-:b([^-/]+)-:c([^-/]+)`) are not affected because they override the default capture group. ### 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-:c` to `/:a-:b([^-/]+)-:c([^-/]+)`. If paths cannot be rewritten and versions cannot be upgraded, another alternative is to limit the URL length. ### References - [GHSA-9wv6-86v2-598j](https://github.com/advisories/GHSA-9wv6-86v2-598j) - [Detailed blog post: ReDoS the web](https://blakeembrey.com/posts/2024-09-web-redos/)

References: https://github.com/pillarjs/path-to-regexp/security/advisories/GHSA-37ch-88jc-xwx2, https://nvd.nist.gov/vuln/detail/CVE-2026-4867, https://blakeembrey.com/posts/2024-09-web-redos, https://cna.openjsf.org/security-advisories.html, https://github.com/advisories/GHSA-9wv6-86v2-598j, https://github.com/pillarjs/path-to-regexp, https://github.com/pillarjs/path-to-regexp/releases/tag/v.0.1.13