CVE-2024-26289: Sigb PMB RCE Vulnerability

CVE-2024-26289 Overview

CVE-2024-26289 is a critical Insecure Deserialization vulnerability affecting PMB (PhpMyBibli), an open-source Integrated Library System (ILS) developed by PMB Services. The vulnerability allows attackers to perform Remote Code Inclusion through deserialization of untrusted data, potentially leading to complete system compromise.

Critical Impact

This vulnerability enables unauthenticated attackers to execute arbitrary code remotely through insecure deserialization, potentially compromising library management systems and associated sensitive data.

Affected Products

• PMB versions 7.5.1 through 7.5.6-2 (exclusive)
• PMB versions 7.4.1 through 7.4.9 (exclusive)
• PMB versions 7.3.1 through 7.3.18 (exclusive)

Discovery Timeline

• 2024-05-27 - CVE CVE-2024-26289 published to NVD
• 2025-04-04 - Last updated in NVD database

Technical Details for CVE-2024-26289

Vulnerability Analysis

This vulnerability falls under CWE-502 (Deserialization of Untrusted Data), a class of security flaws that occurs when an application deserializes data from untrusted sources without proper validation. In the context of PMB, the application accepts serialized PHP objects from user-controllable input and processes them without adequate security checks.

When PHP deserializes objects, it can trigger magic methods such as __wakeup() or __destruct() that may execute arbitrary code if the serialized data contains malicious object chains. Attackers can craft specially designed serialized payloads that, when processed by the vulnerable PMB application, achieve Remote Code Inclusion.

The network-accessible nature of this vulnerability means attackers can exploit it without authentication and without any user interaction, making it particularly dangerous for internet-facing PMB installations.

Root Cause

The root cause of CVE-2024-26289 is the improper handling of serialized data within the PMB application. The application fails to validate or sanitize serialized input before passing it to PHP's deserialization functions. This allows attackers to inject malicious serialized objects that exploit existing class definitions within the application or its dependencies (known as "gadget chains") to achieve code execution.

Attack Vector

The attack vector for this vulnerability is network-based, allowing remote exploitation. An attacker can craft a malicious serialized payload and submit it to the vulnerable PMB endpoint. The exploitation process typically involves:

1. Identifying an endpoint that accepts serialized data
2. Analyzing the application's codebase for exploitable class definitions (gadgets)
3. Constructing a serialized payload that chains these gadgets together
4. Sending the malicious payload to achieve Remote Code Inclusion

The vulnerability does not require authentication or user interaction, and successful exploitation results in high impact to confidentiality, integrity, and availability of the affected system.

For detailed technical analysis and proof-of-concept information, refer to the ENISA Advisory CNW-2024-A-12.

Detection Methods for CVE-2024-26289

Indicators of Compromise

• Unexpected serialized PHP objects in web server logs or request parameters
• Unusual process spawning from the web server or PHP process
• Modified or newly created files in web-accessible directories
• Outbound network connections from the PMB server to unknown destinations
• Web application firewall logs showing serialized object patterns (e.g., O: prefix in parameters)

Detection Strategies

• Deploy Web Application Firewall (WAF) rules to detect and block serialized PHP object patterns in HTTP requests
• Monitor web server access logs for requests containing suspicious serialized data patterns
• Implement file integrity monitoring on PMB installation directories to detect unauthorized modifications
• Enable PHP error logging and monitor for deserialization-related errors or warnings

Monitoring Recommendations

• Configure SIEM alerts for patterns indicative of PHP object injection attacks
• Monitor process execution chains originating from web server processes
• Track file system changes within the PMB web root and temporary directories
• Review outbound network traffic from the PMB server for unusual connections

How to Mitigate CVE-2024-26289

Immediate Actions Required

• Upgrade PMB to version 7.5.6-2 or later for the 7.5.x branch
• Upgrade PMB to version 7.4.9 or later for the 7.4.x branch
• Upgrade PMB to version 7.3.18 or later for the 7.3.x branch
• Restrict network access to PMB installations to trusted IP ranges where possible
• Review server logs for any signs of exploitation attempts

Patch Information

PMB Services has released patched versions that address this deserialization vulnerability. Organizations should download the latest secure versions from the PMB Project Files repository. The fixed versions are:

• 7.5.6-2 and later for the 7.5.x branch
• 7.4.9 and later for the 7.4.x branch
• 7.3.18 and later for the 7.3.x branch

Workarounds

• Implement network-level access controls to restrict access to PMB from untrusted networks
• Deploy a Web Application Firewall with rules to block serialized PHP object injection attempts
• If possible, disable any unnecessary endpoints that accept serialized data
• Place the PMB application behind a reverse proxy with request filtering capabilities

# Example: Apache configuration to restrict access
<Location "/pmb">
    Require ip 10.0.0.0/8
    Require ip 192.168.0.0/16
</Location>