CVE-2021-37701 Information

Description

The npm package ar\ (aka node-tar) before versions 4.4.16 5.0.8 and 6.1.7 has an arbitrary file creation/overwrite and arbitrary code execution vulnerability. 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 where the symlink and directory names in the archive entry used backslashes as a path separator on posix systems. The cache checking logic used both \ and / characters as path separators however \ is a valid filename character on posix systems. 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. Additionally a similar confusion could arise on case-insensitive filesystems. If a tar archive contained a directory at FOO followed by a symbolic link named foo then on case-insensitive file systems the creation of the symbolic link would remove the directory from the filesystem but not from the internal directory cache as it would not be treated as a cache hit. A subsequent file entry within the FOO directory would then be placed in the target of the symbolic link thinking that the directory had already been created. These issues were addressed in releases 4.4.16 5.0.8 and 6.1.7. The v3 branch of node-tar has been deprecated and did not receive patches for these issues. If you are still using a v3 release we recommend you update to a more recent version of node-tar. If this is not possible a workaround is available in the referenced GHSA-9r2w-394v-53qc.

CVSS Vector

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

Reference

https://github.com/npm/node-tar/security/advisories/GHSA-9r2w-394v-53qc https://www.npmjs.com/package/tar https://www.oracle.com/security-alerts/cpuoct2021.html https://www.debian.org/security/2021/dsa-5008 https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

REQUIRED

Confidentiality Impact

CHANGED

Integrity Impact

HIGH

Availability Impact

HIGH

Base Score

HIGH

Base Severity

8.6