CVE-2011-2520 in system-config-firewall
Summary
by MITRE
fw_dbus.py in system-config-firewall 1.2.29 and earlier uses the pickle Python module unsafely during D-Bus communication between the GUI and the backend, which might allow local users to gain privileges via a crafted serialized object.
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Analysis
by VulDB Data Team • 01/12/2025
The vulnerability identified as CVE-2011-2520 resides within the fw_dbus.py component of system-config-firewall version 1.2.29 and earlier. This flaw represents a critical security weakness that exploits unsafe usage of the Python pickle module during D-Bus communication between the graphical user interface and the underlying backend firewall management system. The vulnerability specifically targets the serialization and deserialization processes that occur when exchanging data between the GUI frontend and the system firewall daemon, creating an attack surface where malicious actors can manipulate serialized objects to execute arbitrary code with elevated privileges.
The technical implementation of this vulnerability stems from the insecure handling of pickle module operations within the D-Bus communication pathway. When the system-config-firewall GUI interacts with the backend firewall daemon through D-Bus, it relies on the pickle module to serialize and deserialize data structures for transmission. However, the pickle module in Python is inherently unsafe when processing untrusted data, as it can execute arbitrary code during the deserialization process. This unsafe usage creates a privilege escalation vector where local attackers can craft malicious serialized objects that, when processed by the vulnerable fw_dbus.py script, result in code execution with the privileges of the firewall daemon process. The vulnerability aligns with CWE-502, which specifically addresses "Deserialization of Untrusted Data" and represents a classic example of insecure deserialization leading to arbitrary code execution.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential system compromise and complete loss of firewall protection. Since the firewall daemon typically operates with root privileges, successful exploitation allows attackers to gain full administrative control over the system's network security policies. This includes the ability to modify firewall rules, disable security protections, and potentially establish persistent backdoors. The attack requires local system access, making it particularly dangerous in environments where untrusted users might have login privileges, as it provides a direct path to system compromise. The vulnerability's exploitation aligns with ATT&CK technique T1059.006 for Python and T1068 for privilege escalation, representing a sophisticated attack vector that leverages legitimate system components to bypass security controls.
Mitigation strategies for this vulnerability must address both the immediate security risk and prevent future occurrences of similar flaws. The most effective immediate solution involves upgrading to system-config-firewall version 1.2.30 or later, which contains the necessary patches to eliminate the unsafe pickle usage. Organizations should also implement additional security measures such as restricting local user access where possible, monitoring D-Bus communication for suspicious patterns, and employing principle of least privilege for firewall daemon processes. The fix should replace the pickle module with safer serialization methods such as JSON or XML, which do not execute arbitrary code during deserialization. Security teams should also conduct comprehensive audits of all Python applications using D-Bus communication to identify and remediate similar unsafe serialization patterns, as this vulnerability demonstrates the importance of secure coding practices in inter-process communication mechanisms.