CVE-2025-61168: Sigb Pmb RCE Vulnerability

CVE-2025-61168 Overview

CVE-2025-61168 is a critical insecure deserialization vulnerability affecting SIGB PMB, an open-source library management system. The vulnerability exists in the cms_rest.php component of SIGB PMB version 8.0.1.14, which allows attackers to execute arbitrary code by exploiting unsafe deserialization of user-controlled input. This flaw enables remote attackers to achieve full system compromise without requiring authentication.

Critical Impact

This vulnerability allows unauthenticated remote attackers to execute arbitrary code on affected SIGB PMB installations, potentially leading to complete server compromise, data theft, and lateral movement within organizational networks.

Affected Products

• SIGB PMB v8.0.1.14
• Potentially earlier versions of SIGB PMB (unconfirmed)

Discovery Timeline

• 2025-11-25 - CVE-2025-61168 published to NVD
• 2025-12-01 - Last updated in NVD database

Technical Details for CVE-2025-61168

Vulnerability Analysis

The vulnerability is classified as CWE-502 (Deserialization of Untrusted Data). In PHP applications, insecure deserialization occurs when the unserialize() function processes untrusted input without proper validation. When a malicious serialized object is passed to this function, it can trigger arbitrary code execution through PHP's magic methods such as __wakeup(), __destruct(), or __toString().

The cms_rest.php component in SIGB PMB fails to properly validate or sanitize input before deserializing it. This allows an attacker to craft a malicious serialized payload that, when processed by the vulnerable endpoint, executes arbitrary PHP code with the privileges of the web server process.

The network-accessible nature of this vulnerability combined with no authentication requirements makes it particularly dangerous for internet-facing PMB installations. Successful exploitation grants attackers the ability to read sensitive library data, modify database contents, install backdoors, or pivot to other systems on the network.

Root Cause

The root cause of this vulnerability is the unsafe use of PHP's unserialize() function on user-supplied input within the cms_rest.php component. The application accepts serialized data from external sources without implementing proper input validation, allowlisting of permitted classes, or other protective measures that would prevent malicious object instantiation.

Attack Vector

The attack is conducted over the network by sending specially crafted HTTP requests to the vulnerable cms_rest.php endpoint. An attacker constructs a malicious serialized PHP object containing a payload designed to execute arbitrary commands. When the PMB application deserializes this malicious input, it triggers code execution through gadget chains present in the application or its dependencies.

The attack requires no prior authentication and can be performed by any attacker with network access to the vulnerable PMB installation. A proof-of-concept exploit demonstrating this vulnerability has been published and is available via the GitHub Gist Exploit Code reference.

Detection Methods for CVE-2025-61168

Indicators of Compromise

• Unusual HTTP POST requests to cms_rest.php containing serialized PHP data patterns (strings beginning with O:, a:, s:)
• Web server error logs showing deserialization-related PHP errors or unexpected class instantiation
• Unexpected processes spawned by the web server user (e.g., www-data, apache, nginx)
• New or modified files in the PMB web directory, particularly PHP files that were not part of the original installation
• Outbound network connections from the web server to unusual destinations

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block serialized PHP objects in HTTP request parameters and bodies
• Deploy network intrusion detection signatures that identify PHP deserialization attack patterns targeting cms_rest.php
• Enable verbose logging for the PMB application and monitor for access to the cms_rest.php endpoint from unexpected sources
• Use file integrity monitoring (FIM) to detect unauthorized modifications to PMB installation files

Monitoring Recommendations

• Monitor web server access logs for anomalous requests to cms_rest.php with unusual parameters or large payloads
• Implement alerting on any command execution attempts from the web server process
• Review PHP error logs regularly for deserialization-related warnings or exceptions
• Deploy endpoint detection and response (EDR) solutions to monitor for post-exploitation activity on servers hosting PMB

How to Mitigate CVE-2025-61168

Immediate Actions Required

• Apply the latest security patches from SIGB PMB as documented in the SIGB PMB Security Changelog
• If patching is not immediately possible, restrict network access to the PMB installation using firewall rules or VPN requirements
• Disable or remove the cms_rest.php component if it is not required for operations
• Audit server logs for any signs of previous exploitation attempts

Patch Information

Security updates addressing this vulnerability have been released by SIGB. Administrators should consult the SIGB PMB Security Changelog for detailed patch information and upgrade instructions. Organizations running PMB version 8.0.1.14 should upgrade to the latest available version immediately.

Workarounds

• Implement IP-based access controls to limit access to the cms_rest.php endpoint to trusted networks only
• Deploy a Web Application Firewall (WAF) configured to block requests containing serialized PHP objects
• If the CMS REST functionality is not required, rename or remove the cms_rest.php file temporarily until patching can be completed
• Place the PMB installation behind a reverse proxy that performs request filtering and input sanitization

For environments where the cms_rest.php component must remain accessible, consider implementing additional access controls at the web server level. Below is an example Apache configuration to restrict access:

# Restrict access to cms_rest.php to trusted IPs only
<Location /cms_rest.php>
    Require ip 192.168.1.0/24
    Require ip 10.0.0.0/8
</Location>