CVE-2017-20207

Comprehensive Technical Analysis of CVE-2017-20207

1. Vulnerability Assessment and Severity Evaluation

CVE ID: CVE-2017-20207 CVSS Score: 9.8

The vulnerability in the Flickr Gallery plugin for WordPress, identified as CVE-2017-20207, is classified as a PHP Object Injection vulnerability. This type of vulnerability is particularly severe due to its potential for unauthenticated attackers to execute arbitrary code on the affected server. The CVSS score of 9.8 underscores the critical nature of this vulnerability, indicating a high risk to systems running the affected plugin.

2. Potential Attack Vectors and Exploitation Methods

Attack Vector:

• Unauthenticated Attack: The vulnerability allows unauthenticated attackers to exploit the plugin by injecting malicious PHP objects via the pager parameter.
• Deserialization: The attack leverages the deserialization of untrusted input, which can lead to the injection of a PHP Object.

Exploitation Methods:

• PHP Object Injection: Attackers can craft a specially designed input that, when deserialized, can execute arbitrary code.
• Backdoor Creation: Exploitation of this vulnerability has been observed to create backdoors using the WP_Theme() class, allowing persistent access to the compromised system.

3. Affected Systems and Software Versions

Affected Software:

• Flickr Gallery plugin for WordPress

Affected Versions:

• Versions up to and including 1.5.2

Systems at Risk:

• Any WordPress installation using the Flickr Gallery plugin within the affected version range.

4. Recommended Mitigation Strategies

Immediate Actions:

• Update the Plugin: Ensure that the Flickr Gallery plugin is updated to a version higher than 1.5.2.
• Disable the Plugin: If an update is not immediately available, consider disabling the plugin to mitigate risk.

Long-Term Strategies:

• Regular Updates: Implement a regular update schedule for all plugins and themes to ensure they are patched against known vulnerabilities.
• Code Review: Conduct thorough code reviews and security audits of third-party plugins before deployment.
• Web Application Firewall (WAF): Deploy a WAF to monitor and block suspicious activities, including attempts to exploit known vulnerabilities.

5. Impact on Cybersecurity Landscape

Broader Implications:

• Supply Chain Risk: This vulnerability highlights the risks associated with third-party plugins and the importance of vetting and regularly updating them.
• Exploitation Trends: The active exploitation of this vulnerability underscores the need for proactive monitoring and rapid response to emerging threats.
• Code Quality: Emphasizes the need for secure coding practices, particularly around input validation and deserialization processes.

6. Technical Details for Security Professionals

Vulnerability Details:

• Deserialization Issue: The vulnerability arises from the deserialization of untrusted input from the pager parameter, which can be manipulated to inject a PHP Object.
• Exploitation Payload: Attackers can craft a payload that, when deserialized, triggers the injection of a PHP Object, leading to arbitrary code execution.

Detection and Response:

• Log Analysis: Monitor server logs for unusual activities, particularly those related to the pager parameter.
• Intrusion Detection Systems (IDS): Implement IDS rules to detect and alert on suspicious deserialization attempts.
• Incident Response: Have a well-defined incident response plan in place to quickly address and mitigate any detected exploitation attempts.

Code Example (for illustration purposes):

// Vulnerable code snippet (hypothetical)
$pager = unserialize($_GET['pager']);

// Secure code snippet
if (is_string($_GET['pager'])) {
    $pager = json_decode($_GET['pager'], true);
    // Additional validation and sanitization
}

Conclusion: CVE-2017-20207 represents a critical vulnerability that underscores the importance of secure coding practices and regular updates. Organizations should prioritize updating affected plugins and implementing robust security measures to mitigate similar risks in the future.

References:

• WordPress Plugin Changeset
• Wordfence Blog
• Wordfence Threat Intel