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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

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N

EPSS score

0.064%
(30th percentile)

Weaknesses

CVE ID

CVE-2023-35931

GHSA ID

GHSA-3g7p-8qhx-mc8r
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