Vulnerabilities > CVE-2021-32804 - Path Traversal vulnerability in multiple products
Summary
The npm package "tar" (aka node-tar) before versions 6.1.1, 5.0.6, 4.4.14, and 3.3.2 has a arbitrary File Creation/Overwrite vulnerability due to insufficient absolute path sanitization. node-tar aims to prevent extraction of absolute file paths by turning absolute paths into relative paths when the `preservePaths` flag is not set to `true`. This is achieved by stripping the absolute path root from any absolute file paths contained in a tar file. For example `/home/user/.bashrc` would turn into `home/user/.bashrc`. This logic was insufficient when file paths contained repeated path roots such as `////home/user/.bashrc`. `node-tar` would only strip a single path root from such paths. When given an absolute file path with repeating path roots, the resulting path (e.g. `///home/user/.bashrc`) would still resolve to an absolute path, thus allowing arbitrary file creation and overwrite. This issue was addressed in releases 3.2.2, 4.4.14, 5.0.6 and 6.1.1. Users may work around this vulnerability without upgrading by creating a custom `onentry` method which sanitizes the `entry.path` or a `filter` method which removes entries with absolute paths. See referenced GitHub Advisory for details. Be aware of CVE-2021-32803 which fixes a similar bug in later versions of tar.
Vulnerable Configurations
Common Weakness Enumeration (CWE)
Common Attack Pattern Enumeration and Classification (CAPEC)
- Relative Path Traversal An attacker exploits a weakness in input validation on the target by supplying a specially constructed path utilizing dot and slash characters for the purpose of obtaining access to arbitrary files or resources. An attacker modifies a known path on the target in order to reach material that is not available through intended channels. These attacks normally involve adding additional path separators (/ or \) and/or dots (.), or encodings thereof, in various combinations in order to reach parent directories or entirely separate trees of the target's directory structure.
- Directory Traversal An attacker with access to file system resources, either directly or via application logic, will use various file path specification or navigation mechanisms such as ".." in path strings and absolute paths to extend their range of access to inappropriate areas of the file system. The attacker attempts to either explore the file system for recon purposes or access directories and files that are intended to be restricted from their access. Exploring the file system can be achieved through constructing paths presented to directory listing programs, such as "ls" and 'dir', or through specially crafted programs that attempt to explore the file system. The attacker engaging in this type of activity is searching for information that can be used later in a more exploitive attack. Access to restricted directories or files can be achieved through modification of path references utilized by system applications.
- File System Function Injection, Content Based An attack of this type exploits the host's trust in executing remote content including binary files. The files are poisoned with a malicious payload (targeting the file systems accessible by the target software) by the attacker and may be passed through standard channels such as via email, and standard web content like PDF and multimedia files. The attacker exploits known vulnerabilities or handling routines in the target processes. Vulnerabilities of this type have been found in a wide variety of commercial applications from Microsoft Office to Adobe Acrobat and Apple Safari web browser. When the attacker knows the standard handling routines and can identify vulnerabilities and entry points they can be exploited by otherwise seemingly normal content. Once the attack is executed, the attackers' program can access relative directories such as C:\Program Files or other standard system directories to launch further attacks. In a worst case scenario, these programs are combined with other propagation logic and work as a virus.
- Using Slashes and URL Encoding Combined to Bypass Validation Logic This attack targets the encoding of the URL combined with the encoding of the slash characters. An attacker can take advantage of the multiple way of encoding an URL and abuse the interpretation of the URL. An URL may contain special character that need special syntax handling in order to be interpreted. Special characters are represented using a percentage character followed by two digits representing the octet code of the original character (%HEX-CODE). For instance US-ASCII space character would be represented with %20. This is often referred as escaped ending or percent-encoding. Since the server decodes the URL from the requests, it may restrict the access to some URL paths by validating and filtering out the URL requests it received. An attacker will try to craft an URL with a sequence of special characters which once interpreted by the server will be equivalent to a forbidden URL. It can be difficult to protect against this attack since the URL can contain other format of encoding such as UTF-8 encoding, Unicode-encoding, etc.
- Manipulating Input to File System Calls An attacker manipulates inputs to the target software which the target software passes to file system calls in the OS. The goal is to gain access to, and perhaps modify, areas of the file system that the target software did not intend to be accessible.
References
- https://www.npmjs.com/advisories/1770
- https://github.com/npm/node-tar/commit/1f036ca23f64a547bdd6c79c1a44bc62e8115da4
- https://github.com/npm/node-tar/security/advisories/GHSA-3jfq-g458-7qm9
- https://www.npmjs.com/package/tar
- https://www.oracle.com/security-alerts/cpuoct2021.html
- https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf