Shescape is a simple shell escape package for JavaScript. Versions prior to 1.5.8 were found to be subject to code injection on windows. This impacts users that use Shescape (any API function) to escape arguments for cmd.exe on Windows An attacker can omit all arguments following their input by including a line feed character ('\n') in the payload. This bug has been patched in [v1.5.8] which you can upgrade to now. No further changes are required. Alternatively, line feed characters ('\n') can be stripped out manually or the user input can be made the last argument (this only limits the impact).

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 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.

Shescape is a simple shell escape library for JavaScript. Prior to 2.1.14 and 3.0.1, getEscapeFunction in src/internal/win/cmd.js does not escape ( and ) when applications use the escape or escapeAll APIs on Windows with shell set to cmd.exe, or with shell set to true when CMD is the default. An attacker-controlled argument can break out of a parenthesized CMD construct and inject shell syntax depending on the original command, resulting in arbitrary command execution. This issue is fixed in versions 2.1.14 and 3.0.1.

Impact

This may impact users that use Shescape on Windows in a threaded context (e.g. using Worker threads). The vulnerability can result in Shescape escaping (or quoting) for the wrong shell, thus allowing attackers to bypass protections depending on the combination of expected and used shell.

This snippet demonstrates a vulnerable use of Shescape:

javascript // vulnerable.js

import { exec } from "node:childprocess"; import { Worker, isMainThread } from 'node:workerthreads';

import as shescape from "shescape";

if (isMainThread) { // 1. Something like a worker thread must be used. The reason being that they // unexpectedly change environment variable names on Windows. new Worker("./vulnerable.js"); } else { // 2. Example configuration that's problematic. In this setup example the // expected default system shell is CMD. We configure the use of PowerShell. // Shescape will fail to look up PowerShell and default to escaping for CMD // instead, resulting in the vulnerability. const options = { shell: "powershell", interpolation: true, };

// 3. Using shescape to protect against attacks, this is correct. const escaped = shescape.escape("&& ls", options);

// 4. Invoking a command with the escaped user input, this is vulnerable in // this case. exec(echo Hello ${escaped}, options, (error, stdout) => { if (error) { console.error(An error occurred: ${error}); } else { console.log(stdout); } }); }

Patches

This bug has been patched in v1.7.4 which you can upgrade to now. No further changes are required.

Workarounds

If you are impacted there is no workaround possible.

References

- Shescape Pull Request #1142 - Shescape commit 0b976da - Shescape release v1.7.4

For more information

- Comment on Pull Request #1142 - Comment on commit 0b976da - Open an issue at https://github.com/ericcornelissen/shescape/issues (New issue > Question > Get started)

shescape is a simple shell escape package for JavaScript. In shescape before version 1.1.3, anyone using Shescape to defend against shell injection may still be vulnerable against shell injection if the attacker manages to insert a into the payload. For an example see the referenced GitHub Security Advisory. The problem has been patched in version 1.1.3. No further changes are required.

Shescape is a shell escape package for JavaScript. An Inefficient Regular Expression Complexity vulnerability impacts users that use Shescape to escape arguments for the Unix shells Bash and Dash, or any not-officially-supported Unix shell; and/or using the escape or escapeAll functions with the interpolation option set to true. An attacker can cause polynomial backtracking or quadratic runtime in terms of the input string length due to two Regular Expressions in Shescape that are vulnerable to Regular Expression Denial of Service (ReDoS). This bug has been patched in v1.5.10. For Dash only, this bug has been patched since v1.5.9. As a workaround, a maximum length can be enforced on input strings to Shescape to reduce the impact of the vulnerability. It is not recommended to try and detect vulnerable input strings, as the logic for this may end up being vulnerable to ReDoS itself.

Impact

This impacts users that use shescape to escape arguments:

- for the Unix shell Bash, or any not-officially-supported Unix shell; - using the escape or escapeAll functions with the interpolation option set to true.

An attacker can cause polynomial backtracking in terms of the input string length due to a Regular Expression in shescape that is vulnerable to Regular Expression Denial of Service (ReDoS). Example:

javascript import as shescape from "shescape";

/ 1. Prerequisites / const options = { interpolation: true, // and shell: "/bin/bash", // or shell: "some-not-officially-supported-shell", // or shell: undefined, // Only if the system's default shell is bash or an unsupported shell. };

/ 2. Attack / let userInput = '{,'.repeat(150000); // polynomial backtracking

/ 3. Usage / shescape.escape(userInput, options); // or shescape.escapeAll([userInput], options);

Patches

This bug has been patched in v1.6.1 which you can upgrade to now. No further changes required.

Workarounds

Alternatively, a maximum length can be enforced on input strings to shescape to reduce the impact of the vulnerability. It is not recommended to try and detect vulnerable input strings, as the logic for this may end up being vulnerable to ReDoS itself.

References

- Shescape commit 552e8ea - Shescape Release v1.6.1

For more information

- Comment on commit 552e8ea - Open an issue at https://github.com/ericcornelissen/shescape/issues (New issue > Question > Get started)

Shescape is a simple shell escape library for JavaScript. Prior to 2.1.14 and 3.0.1, this impacts users of Shescape on Unix systems that explicitly configure shell to Zsh, or true when the default shell is Zsh, using the escape and escapeAll. The Zsh options EXTENDEDGLOB and MAGICEQUALSUBST exacerbate the problem. In certain case, an attacker can leverage home directory expansion and extended glob syntax to obtain lists of files and directories on the system. Depending on what the command does, this may be used to leak more information. This issue is fixed in versions 2.1.14 and 3.0.1.

Shescape before 2.1.15 (and 3.0.0 before 3.0.2) fails to properly escape tilde (~) characters in assignment contexts on Unix systems where the shell is explicitly configured to "sh" or true and /bin/sh points to BusyBox. Using the escape and escapeAll APIs with untrusted input in an assignment prefixed to a command, an attacker can inject a tilde payload to disclose the user's home directory location and, depending on usage, alter the location on which a command operates.

Shescape is a shell escape package for JavaScript. An issue in versions 1.4.0 to 1.5.1 allows for exposure of the home directory on Unix systems when using Bash with the escape or escapeAll functions from the shescape API with the interpolation option set to true. Other tested shells, Dash and Zsh, are not affected. Depending on how the output of shescape is used, directory traversal may be possible in the application using shescape. The issue was patched in version 1.5.1. As a workaround, manually escape all instances of the tilde character (~) using arg.replace(/~/g, "\\~").