GHSA-37ch-88jc-xwx2 path-to-regexp vulnerable to Regular Expression Denial of Service via multiple route parameters

• npm path-to-regexp: < 0.1.13 → fixed in 0.1.13

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] 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 • Detailed blog post: ReDoS the web