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Shescape potential environment variable exposure on Windows with CMD

Low severity GitHub Reviewed Published Jun 22, 2023 in ericcornelissen/shescape • Updated Nov 7, 2023

Package

npm shescape (npm)

Affected versions

< 1.7.1

Patched versions

1.7.1

Description

Impact

This impact users of Shescape:

  1. On Windows using the Windows Command Prompt (i.e. cmd.exe), and
  2. Using quote/quoteAll or escape/escapeAll with the interpolation option set to true.

An attacker may be able to get read-only access to environment variables. Example:

import * as cp from "node:child_process";
import * as shescape from "shescape";

// 1. Prerequisites
const options = {
    shell: "cmd.exe",
    // Or
    shell: undefined, // Only if the default shell is CMD

    // And
    interpolation: true, // Only applies to `escape` and `escapeAll` usage
}

// 2. Attack (one of many)
const payload = "%PATH%";

// 3. Usage
let escapedPayload;

escapedPayload = shescape.quote(payload, options);
// Or
escapedPayload = shescape.quoteAll([payload], options);
// Or
escapedPayload = shescape.escape(payload, options);
// Or
escapedPayload = shescape.escapeAll([payload], options);

// And (example)
const result = cp.execSync(`echo Hello ${escapedPayload}`, options);

// 4. Impact
console.log(result.toString());
// Outputs "Hello" followed by the contents of the PATH environment variable

Patches

This bug has been patched in v1.7.1 which you can upgrade to now. No further changes are required.

Workarounds

Alternatively, users can remove all instances of % from user input, either before or after using Shescape.

References

References

Published to the GitHub Advisory Database Jun 22, 2023
Reviewed Jun 22, 2023
Published by the National Vulnerability Database Jun 23, 2023
Last updated Nov 7, 2023

Severity

Low
3.1
/ 10

CVSS base metrics

Attack vector
Network
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N

Weaknesses

CVE ID

CVE-2023-35931

GHSA ID

GHSA-3g7p-8qhx-mc8r
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