Ecosyste.ms: Advisories

Security Advisories: GSA_kwCzR0hTQS1jcjg0LXh2dzQtcXgzY84AAvio

Inefficient Regular Expression Complexity in shescape

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:

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(150_000); // 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)

Permalink: https://github.com/advisories/GHSA-cr84-xvw4-qx3c
JSON: https://advisories.ecosyste.ms/api/v1/advisories/GSA_kwCzR0hTQS1jcjg0LXh2dzQtcXgzY84AAvio
Source: GitHub Advisory Database
Origin: Unspecified
Severity: High
Classification: General
Published: about 2 years ago
Updated: about 1 year ago

CVSS Score: 7.5
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Percentage: 0.00174
EPSS Percentile: 0.54698

Identifiers: GHSA-cr84-xvw4-qx3c, CVE-2022-25918
References:

• https://github.com/ericcornelissen/shescape/security/advisories/GHSA-cr84-xvw4-qx3c
• https://nvd.nist.gov/vuln/detail/CVE-2022-25918
• https://github.com/ericcornelissen/shescape/commit/552e8eab56861720b1d4e5474fb65741643358f9
• https://github.com/ericcornelissen/shescape/blob/main/src/unix.js%23L52
• https://github.com/ericcornelissen/shescape/releases/tag/v1.6.1
• https://security.snyk.io/vuln/SNYK-JS-SHESCAPE-3061108
• https://github.com/advisories/GHSA-cr84-xvw4-qx3c

Repository: https://github.com/ericcornelissen/shescape
Blast Radius: 10.9

Affected Packages