CVE-2006-6876 in OpenSER
Summary
by MITRE
Buffer overflow in the fetchsms function in the SMS handling module (libsms_getsms.c) in OpenSER 1.2.0 and earlier allows remote attackers to cause a denial of service (crash) via a crafted SMS message, triggering memory corruption when the "beginning" buffer is copied to the third (pdu) argument.
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Analysis
by VulDB Data Team • 03/26/2019
The vulnerability identified as CVE-2006-6876 represents a critical buffer overflow flaw within the OpenSER communication server version 1.2.0 and earlier. This issue resides in the SMS handling module specifically within the fetchsms function located in the libsms_getsms.c file. The flaw manifests when the system processes incoming SMS messages, creating a pathway for remote attackers to exploit the software through carefully crafted malicious payloads. The vulnerability operates by manipulating the buffer copying mechanism between different memory segments, specifically targeting the "beginning" buffer and its transfer to the third argument designated as pdu. This particular implementation flaw creates a scenario where the system fails to properly validate buffer boundaries during SMS message processing, leading to memory corruption that ultimately results in system instability.
The technical exploitation of this vulnerability follows a well-defined pattern that aligns with common buffer overflow attack methodologies. When a malicious SMS message is received, the fetchsms function attempts to copy data from an initial buffer location to a destination buffer parameter named pdu. Due to insufficient boundary checking and input validation, the copy operation exceeds the allocated memory space, causing memory corruption that leads to program termination. This type of vulnerability falls under the CWE-121 category of stack-based buffer overflow, where the system's memory management fails to properly constrain data movement between different buffer regions. The attack vector is particularly dangerous as it requires no authentication or privileged access, making it a remote code execution threat that can be exploited over network connections.
The operational impact of this vulnerability extends beyond simple denial of service conditions, creating potential security risks for systems relying on OpenSER for communication services. When exploited successfully, the buffer overflow causes the OpenSER application to crash and terminate unexpectedly, disrupting SMS messaging services and potentially affecting other communication functions that depend on the server. The crash behavior can be leveraged by attackers to create persistent service disruptions, making this vulnerability particularly concerning for organizations that depend on reliable communication infrastructure. The vulnerability's remote exploitation capability means that attackers can trigger the crash from any location without requiring physical access to the system, increasing the attack surface and making the vulnerability more accessible to a broader range of threat actors.
Mitigation strategies for CVE-2006-6876 should focus on immediate patching of the OpenSER software to version 1.2.1 or later, where the buffer overflow has been addressed through proper input validation and boundary checking mechanisms. Organizations should implement network segmentation and access controls to limit exposure to the vulnerable SMS handling module, particularly in environments where external SMS traffic is processed. Additionally, deploying intrusion detection systems that can monitor for suspicious SMS message patterns may help identify potential exploitation attempts. The implementation of proper input sanitization and memory boundary checks in the SMS handling code represents the fundamental solution to this vulnerability. Security teams should also consider implementing application-level monitoring to detect abnormal termination patterns and establish incident response procedures specifically addressing denial of service attacks targeting communication servers. Organizations utilizing older versions of OpenSER should prioritize upgrading to supported releases that contain the necessary security patches to prevent exploitation of this and similar vulnerabilities.