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githubGitHub Advisory DatabaseGHSA-GMW6-94GG-2RC2
HistoryAug 31, 2021 - 4:03 p.m.

UNIX Symbolic Link (Symlink) Following in @npmcli/arborist

2021-08-3116:03:34
CWE-59
CWE-61
GitHub Advisory Database
github.com
20
unix
symbolic link
symlink
arborist
npm
dependency
file system
symbolic link mitigation
patch
untrusted code
package
verification
directory
development environment

CVSS2

4.4

Attack Vector

LOCAL

Attack Complexity

MEDIUM

Authentication

NONE

Confidentiality Impact

PARTIAL

Integrity Impact

PARTIAL

Availability Impact

PARTIAL

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

CVSS3

8.2

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

REQUIRED

Scope

CHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

NONE

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

EPSS

0.001

Percentile

28.6%

Impact

Arbitrary File Creation, Arbitrary File Overwrite, Arbitrary Code Execution

@npmcli/arborist, the library that calculates dependency trees and manages the node_modules folder hierarchy for the npm command line interface, aims to guarantee that package dependency contracts will be met, and the extraction of package contents will always be performed into the expected folder.

This is accomplished by extracting package contents into a projectโ€™s node_modules folder.

If the node_modules folder of the root project or any of its dependencies is somehow replaced with a symbolic link, it could allow Arborist to write package dependencies to any arbitrary location on the file system.

Note that symbolic links contained within package artifact contents are filtered out, so another means of creating a node_modules symbolic link would have to be employed.

  1. A preinstall script could replace node_modules with a symlink. (This is prevented by using --ignore-scripts.)
  2. An attacker could supply the target with a git repository, instructing them to run npm install --ignore-scripts in the root. This may be successful, because npm install --ignore-scripts is typically not capable of making changes outside of the project directory, so it may be deemed safe.

Patches

2.8.2 (included in npm v7.20.7 and above)

Workarounds

Do not run npm install on untrusted codebases, without first ensuring that the node_modules directory in the project is not a symbolic link.

Fix

Prior to extracting any package contents, the node_modules folder into which it is extracted is verified to be a real directory. If it is not, then it is removed.

Caveat: if you are currently relying on creating a symbolic link to the node_modules folder in order to share dependencies between projects, then that will no longer be possible. Please use the npm link command, explicit file:... dependencies, and/or workspaces to share dependencies in a development environment.

Affected configurations

Vulners
Node
npmcliarboristRange<2.8.2
VendorProductVersionCPE
npmcliarborist*cpe:2.3:a:npmcli:arborist:*:*:*:*:*:*:*:*

CVSS2

4.4

Attack Vector

LOCAL

Attack Complexity

MEDIUM

Authentication

NONE

Confidentiality Impact

PARTIAL

Integrity Impact

PARTIAL

Availability Impact

PARTIAL

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

CVSS3

8.2

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

REQUIRED

Scope

CHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

NONE

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

EPSS

0.001

Percentile

28.6%