npmjs tar CVE-2021-37701 vulnerability in Npmjs and Other Products
Published on August 31, 2021

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

product logo product logo product logo product logo
The npm package "tar" (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.

Github Repository Vendor Advisory NVD

Vulnerability Analysis

CVE-2021-37701 can be exploited with local system access, requires user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality and integrity, and no impact on availability.

Attack Vector:
LOCAL
Attack Complexity:
LOW
Privileges Required:
NONE
User Interaction:
REQUIRED
Scope:
CHANGED
Confidentiality Impact:
HIGH
Integrity Impact:
HIGH
Availability Impact:
NONE

Weakness Types

What is a Directory traversal Vulnerability?

The software uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the software does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

CVE-2021-37701 has been classified to as a Directory traversal vulnerability or weakness.

What is an insecure temporary file Vulnerability?

The software attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

CVE-2021-37701 has been classified to as an insecure temporary file vulnerability or weakness.


Products Associated with CVE-2021-37701

You can be notified by email with stack.watch whenever vulnerabilities like CVE-2021-37701 are published in these products:

Npmjs Tar
 
Debian Linux
 
Oracle GraalVM
 
Siemens Sinec Infrastructure Network Services
 

Affected Versions

npm node-tar:

Vulnerable Packages

The following package name and versions may be associated with CVE-2021-37701

Package Manager Vulnerable Package Versions Fixed In
npm tar >= 6.0.0, < 6.1.7 6.1.7
npm tar >= 5.0.0, < 5.0.8 5.0.8
npm tar < 4.4.16 4.4.16

Exploit Probability

EPSS
0.03%
Percentile
6.59%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.