Netskope, a leading provider of cloud security solutions, recently disclosed a vulnerability in its Netskope Client. This vulnerability allows an authenticated local attacker to access sensitive information found in NSClient logs. Sensitive data should not be logged as it can provide attackers with valuable information for launching further attacks, such as downloading data and impersonating other users.

In this post, we'll delve into the vulnerability's details and explore possible ways to mitigate or remediate the issue. We'll also walk through an example exploit scenario to help you understand the potential impacts of the vulnerability and how a local attacker could exploit it.

Vulnerability Details

CVE number: CVE-2021-44862
Affected software: Netskope Client
Vulnerability type: Sensitive data exposure, Information disclosure
Impact: View sensitive information stored in NSClient logs
Attack mode: Authenticated, local access

When the Netskope Client processes certain items that contain sensitive information, such as user affiliations, tokens, or credentials, the information is saved unmasked in the NSClient logs. This information could be retrieved and used by a skilled attacker for various malicious activities.

Here's a code snippet demonstrating the vulnerability

// NetskopeClientLogParser.php

function parseLog($logText) {
    ...
    $userAffiliation = extractUserAffiliation($logData);
    $authToken = extractAuthToken($logData);

    // The following lines write the sensitive data as plain text to the log
    $logEntry = "User affiliation: " . $userAffiliation . "; Auth token: " . $authToken;
    writeToLogFile($logEntry);

    ...
}

Exploit Scenario

1. A malicious user with local access to a Netskope client installs a log-monitoring tool to track the NSClient log file's content continuously.
2. The user begins running the Netskope application, causing the log file to be updated with plain text-sensitive data, including user affiliations and authentication tokens.
3. The attacker leverages the log-monitoring tool to capture the sensitive information and uses it to download confidential data or impersonate another user, leading to a potential data breach or credential compromise.

Here are some informative resources related to CVE-2021-44862.

1. CVE-2021-44862 - NVD - https://nvd.nist.gov/vuln/detail/CVE-2021-44862
2. Netskope Security Advisory - https://www.netskope.com/security-advisories

Mitigation and Remediation Steps

The ideal solution is to update to the latest Netskope Client, which contains a fix for the vulnerability. If that is not feasible immediately, consider the following options:

1. Restrict NSClient log file permissions: Configure the Netskope client's log file permissions to restrict access to only authorized individuals or groups. This step ensures that any attacker cannot read the log file containing sensitive data.
2. Monitor and filter logs: Implement log-monitoring solutions to alert you to any unauthorized access or attempts to access sensitive log data. You can also configure the log-monitoring tool to filter out sensitive information before saving it to the log file.
3. Establish clear policies and guidelines: Ensure your organization has policies and guidelines on protecting sensitive information and equip employees with tools and practices to detect and report suspicious activities.

Conclusion

CVE-2021-44862 impacts the Netskope Client by allowing authenticated, local attackers to view sensitive information stored in the NSClient's logs. This vulnerability can lead to data breaches, credential compromises, or other malicious activities if the compromised information is misused. However, by updating to the latest Netskope Client and taking the necessary mitigation steps, you can protect your organization from the potential impact of this issue.

Timeline

Published on: 11/03/2022 20:15:00 UTC
Last modified on: 11/04/2022 13:28:00 UTC