Package Instance

path-to-regexp vulnerable to Denial of Service via sequential optional groups
### Impact

A bad regular expression is generated any time you have multiple sequential optional groups (curly brace syntax), such as `{a}{b}{c}:z`. The generated regex grows exponentially with the number of groups, causing denial of service.

### Patches

Fixed in version 8.4.0.

### Workarounds

Limit the number of sequential optional groups in route patterns. Avoid passing user-controlled input as route patterns.

path-to-regexp vulnerable to Regular Expression Denial of Service via multiple wildcards
### Impact

When using multiple wildcards, combined with at least one parameter, a regular expression can be generated that is vulnerable to ReDoS. This backtracking vulnerability requires the second wildcard to be somewhere other than the end of the path.

**Unsafe examples:**

```
/*foo-*bar-:baz
/*a-:b-*c-:d
/x/*a-:b/*c/y
```

**Safe examples:**

```
/*foo-:bar
/*foo-:bar-*baz
```

### Patches

Upgrade to version `8.4.0`.

### Workarounds

If developers are using multiple wildcard parameters, they can check the regex output with a tool such as https://makenowjust-labs.github.io/recheck/playground/ to confirm whether a path is vulnerable.