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cvelistGitHub_MCVELIST:CVE-2021-39134
HistoryAug 31, 2021 - 4:55 p.m.

CVE-2021-39134 UNIX Symbolic Link (Symlink) Following in @npmcli/arborist

2021-08-3116:55:11
CWE-61
GitHub_M
www.cve.org
4

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

AI Score

8.4

Confidence

High

EPSS

0.001

Percentile

28.6%

@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, in part, accomplished by resolving dependency specifiers defined in package.json manifests for dependencies with a specific name, and nesting folders to resolve conflicting dependencies. When multiple dependencies differ only in the case of their name, Arborist’s internal data structure saw them as separate items that could coexist within the same level in the node_modules hierarchy. However, on case-insensitive file systems (such as macOS and Windows), this is not the case. Combined with a symlink dependency such as file:/some/path, this allowed an attacker to create a situation in which arbitrary contents could be written to any location on the filesystem. For example, a package pwn-a could define a dependency in their package.json file such as "foo": "file:/some/path". Another package, pwn-b could define a dependency such as FOO: "file:foo.tgz". On case-insensitive file systems, if pwn-a was installed, and then pwn-b was installed afterwards, the contents of foo.tgz would be written to /some/path, and any existing contents of /some/path would be removed. Anyone using npm v7.20.6 or earlier on a case-insensitive filesystem is potentially affected. This is patched in @npmcli/arborist 2.8.2 which is included in npm v7.20.7 and above.

CNA Affected

[
  {
    "product": "arborist",
    "vendor": "npm",
    "versions": [
      {
        "status": "affected",
        "version": "< 2.8.2"
      }
    ]
  }
]

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

AI Score

8.4

Confidence

High

EPSS

0.001

Percentile

28.6%