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githubGitHub Advisory DatabaseGHSA-R628-MHMH-QJHW
HistoryAug 03, 2021 - 7:00 p.m.

Arbitrary File Creation/Overwrite via insufficient symlink protection due to directory cache poisoning

2021-08-0319:00:40
CWE-22
CWE-23
CWE-59
GitHub Advisory Database
github.com
45

8.1 High

CVSS3

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H

5.8 Medium

CVSS2

Access Vector

NETWORK

Access Complexity

MEDIUM

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

PARTIAL

Availability Impact

PARTIAL

AV:N/AC:M/Au:N/C:N/I:P/A:P

0.006 Low

EPSS

Percentile

78.4%

Impact

Arbitrary File Creation, Arbitrary File Overwrite, Arbitrary Code Execution

node-tar aims to guarantee that any file whose location would be modified by a symbolic link is not extracted. This is, in part, achieved by ensuring that extracted directories are not symlinks. Additionally, in order to prevent unnecessary stat calls to determine whether a given path is a directory, paths are cached when directories are created.

This logic was insufficient when extracting tar files that contained both a directory and a symlink with the same name as the directory. This order of operations resulted in the directory being created and added to the node-tar directory cache. When a directory is present in the directory cache, subsequent calls to mkdir for that directory are skipped. However, this is also where node-tar checks for symlinks occur.

By first creating a directory, and then replacing that directory with a symlink, it was thus possible to bypass node-tar symlink checks on directories, essentially allowing an untrusted tar file to symlink into an arbitrary location and subsequently extracting arbitrary files into that location, thus allowing arbitrary file creation and overwrite.

This issue was addressed in releases 3.2.3, 4.4.15, 5.0.7 and 6.1.2.

Patches

3.2.3 || 4.4.15 || 5.0.7 || 6.1.2

Workarounds

Users may work around this vulnerability without upgrading by creating a custom filter method which prevents the extraction of symbolic links.

const tar = require('tar')

tar.x({
  file: 'archive.tgz',
  filter: (file, entry) => {
    if (entry.type === 'SymbolicLink') {
      return false
    } else {
      return true
    }
  }
})

Users are encouraged to upgrade to the latest patch versions, rather than attempt to sanitize tar input themselves.

CPENameOperatorVersion
tarlt3.2.3
tarlt6.1.2
tarlt5.0.7
tarlt4.4.15

8.1 High

CVSS3

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H

5.8 Medium

CVSS2

Access Vector

NETWORK

Access Complexity

MEDIUM

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

PARTIAL

Availability Impact

PARTIAL

AV:N/AC:M/Au:N/C:N/I:P/A:P

0.006 Low

EPSS

Percentile

78.4%