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GHSA-j55r-787p-m549

HighCVSS 8.6 / 10
Published Aug 22, 2023·Last modified Nov 8, 2023
Affected Components(0)

No affected components available

Description

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:

// vulnerable.js

import { exec } from "node:child_process";
import { Worker, isMainThread } from 'node:worker_threads';

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

For more information

Risk Scores
Base Score
8.6

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the integrity of the data.

Threat Intelligence
7.9

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS
0.56%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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High severity
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