CVE-2022-31180 in Shescape
Summary
by MITRE • 08/02/2022
Shescape is a simple shell escape package for JavaScript. Affected versions were found to have insufficient escaping of white space when interpolating output. This issue only impacts users that use the `escape` or `escapeAll` functions with the `interpolation` option set to `true`. The result is that if an attacker is able to include whitespace in their input they can: 1. Invoke shell-specific behaviour through shell-specific special characters inserted directly after whitespace. 2. Invoke shell-specific behaviour through shell-specific special characters inserted or appearing after line terminating characters. 3. Invoke arbitrary commands by inserting a line feed character. 4. Invoke arbitrary commands by inserting a carriage return character. Behaviour number 1 has been patched in [v1.5.7] which you can upgrade to now. No further changes are required. Behaviour number 2, 3, and 4 have been patched in [v1.5.8] which you can upgrade to now. No further changes are required. The best workaround is to avoid having to use the `interpolation: true` option - in most cases using an alternative is possible, see [the recipes](https://github.com/ericcornelissen/shescape#recipes) for recommendations. Alternatively, users may strip all whitespace from user input. Note that this is error prone, for example: for PowerShell this requires stripping `'\u0085'` which is not included in JavaScript's definition of `\s` for Regular Expressions.
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Analysis
by VulDB Data Team • 08/02/2022
CVE-2022-31180 represents a critical command injection vulnerability in the shescape JavaScript package that affects versions prior to 1.5.8. This vulnerability stems from inadequate handling of whitespace characters during shell command interpolation, specifically when the interpolation option is enabled. The flaw resides in the package's failure to properly escape whitespace characters that could be exploited to manipulate shell execution behavior. The vulnerability is categorized under CWE-78 as a failure to sanitize shell metacharacters, which directly maps to the core issue of improper input validation in shell command construction.
The technical implementation of this vulnerability allows attackers to manipulate shell behavior through several distinct attack vectors that leverage whitespace character handling. When interpolation is enabled, the package fails to properly escape whitespace characters that can trigger shell-specific behaviors through special characters inserted immediately after whitespace. Additionally, attackers can exploit line terminating characters to invoke shell-specific behaviors, while inserting line feed or carriage return characters enables arbitrary command execution. These attack vectors demonstrate a fundamental weakness in the package's input sanitization approach, where the escaping mechanism does not adequately address all whitespace character variations that could be leveraged for malicious purposes.
The operational impact of this vulnerability extends beyond simple command injection to potentially allow full system compromise when the affected package is used in applications that process user input through shell commands. Attackers who can inject whitespace characters into input data can manipulate shell execution flow and potentially execute unauthorized commands on the system. This vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter, specifically targeting the execution of shell commands through improper input handling. The patching strategy implemented in versions 1.5.7 and 1.5.8 addresses different aspects of the vulnerability, with version 1.5.7 fixing the initial whitespace handling issue and 1.5.8 providing comprehensive protection against all four identified attack vectors.
The recommended mitigation strategy emphasizes avoiding the interpolation option entirely, which aligns with defensive programming principles and the principle of least privilege in security design. This approach directly addresses the root cause of the vulnerability by eliminating the risky functionality altogether. Alternative approaches such as stripping whitespace from user input present their own challenges, particularly with character set handling as demonstrated by the PowerShell example where non-standard whitespace characters like U+0085 require specific handling outside standard JavaScript regex character classes. Organizations should consider implementing input validation and sanitization at multiple layers, including application-level filtering and proper command execution practices that avoid shell interpolation entirely when possible. The vulnerability serves as a reminder of the critical importance of proper input sanitization and the potential consequences of inadequate escaping mechanisms in security-sensitive components.
The broader implications of this vulnerability highlight the importance of security considerations in seemingly simple utility packages that handle shell interactions. This issue demonstrates how common security practices like shell escaping can be undermined by incomplete implementation, particularly when dealing with complex character sets and different shell behaviors. The vulnerability's resolution through version updates emphasizes the importance of maintaining current security libraries and monitoring for security advisories in the software supply chain. Organizations should implement automated dependency scanning and regular security audits to identify and remediate similar vulnerabilities across their software ecosystems. The incident underscores the need for comprehensive security testing that includes edge cases involving character handling, whitespace manipulation, and shell metacharacter interactions.