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doc: clarify path.isAbsolute is not enough for mitigating path traversals #57073

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Merged
aduh95 merged 4 commits into from
Mar 2, 2025
Merged

doc: clarify path.isAbsolute is not enough for mitigating path traversals #57073

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doc: clarify path.isAbsolute doesn’t resolve paths
ericfortis Feb 15, 2025
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doc: clarify path.isAbsolute doesn’t resolve paths
ericfortis Feb 16, 2025
f79fbba
doc: clarify path.isAbsolute doesn’t resolve paths
ericfortis Mar 2, 2025
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doc: clarify path.isAbsolute doesn’t resolve paths
ericfortis Mar 2, 2025
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24 changes: 18 additions & 6 deletions doc/api/path.md
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Original file line number Diff line number Diff line change
Expand Up @@ -317,17 +317,29 @@ added: v0.11.2
* `path` {string}
* Returns: {boolean}

The `path.isAbsolute()` method determines if `path` is an absolute path.
The `path.isAbsolute()` method determines if the literal `path` is absolute.
Therefore, it’s not safe for mitigating path traversals without normalizing it.

```js
// Normalizing the subpath mitigates traversing above the mount directory
const subpath = '/foo/../..'
if (!path.isAbsolute(path.normalize(subpath))) {
throw 'FORBIDDEN'
}
const myPath = path.join(MOUNT_DIR, subpath)
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```


If the given `path` is a zero-length string, `false` will be returned.

For example, on POSIX:
On POSIX:
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```js
path.isAbsolute('/foo/bar'); // true
path.isAbsolute('/baz/..'); // true
path.isAbsolute('qux/'); // false
path.isAbsolute('.'); // false
path.isAbsolute('/foo/bar'); // true
path.isAbsolute('/baz/..'); // true
path.isAbsolute('/baz/../..'); // true
path.isAbsolute('qux/'); // false
path.isAbsolute('.'); // false
```

On Windows:
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