CVE-2013-2238 in FreeSWITCH
Summary
by MITRE
Multiple buffer overflows in the switch_perform_substitution function in switch_regex.c in FreeSWITCH 1.2 allow remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via vectors related to the index and substituted variables.
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Analysis
by VulDB Data Team • 03/27/2019
The vulnerability identified as CVE-2013-2238 represents a critical buffer overflow flaw within the FreeSWITCH telecommunications platform version 1.2. This issue resides in the switch_perform_substitution function located in the switch_regex.c source file, making it a fundamental component of the software's regular expression processing capabilities. The vulnerability affects the core functionality of FreeSWITCH's media processing engine, which handles various telephony operations including call routing, voice processing, and SIP protocol handling. As a telecommunications application, FreeSWITCH serves as a foundational element in VoIP infrastructure, making this vulnerability particularly concerning for organizations relying on its services for mission-critical communications.
The technical implementation of this buffer overflow stems from inadequate input validation within the switch_perform_substitution function that processes regular expression substitutions. When the function handles index and substituted variables, it fails to properly bounds-check the data being processed, allowing malicious input to exceed allocated memory buffers. This flaw operates under CWE-121, which classifies buffer overflow conditions where insufficient checks permit data to overwrite adjacent memory locations. The vulnerability manifests when remote attackers craft specially malformed input strings that trigger the substitution logic, causing the application to write beyond the intended buffer boundaries. The function's handling of variable substitution in regular expressions creates multiple potential attack vectors where attacker-controlled data can influence memory layout and execution flow.
Operationally, this vulnerability creates significant risks for FreeSWITCH deployments as it can be exploited remotely without authentication, making it particularly dangerous for publicly accessible telephony systems. The primary impact involves denial of service through application crashes, which can disrupt critical communication services and potentially lead to complete system unavailability. However, the vulnerability's potential for arbitrary code execution presents an even more severe threat, as attackers could leverage the buffer overflow to gain control of the FreeSWITCH process. This capability allows for privilege escalation within the telephony environment, potentially enabling attackers to intercept communications, modify call routing, or establish persistent access points within network infrastructure. The vulnerability's exploitation requires minimal privileges and can be automated, making it attractive for both casual and sophisticated attackers targeting telecommunications systems.
Organizations using FreeSWITCH 1.2 should prioritize immediate remediation through official security patches provided by the FreeSWITCH project, as this vulnerability has been documented and addressed in subsequent releases. The mitigation strategy should include comprehensive network monitoring to detect potential exploitation attempts and implementation of intrusion detection systems that can identify malformed regular expression patterns targeting this specific function. Additionally, network segmentation and access control measures should be implemented to limit exposure of FreeSWITCH instances to untrusted networks. Security teams should also consider implementing runtime protections such as address space layout randomization and stack canaries to reduce exploit reliability. The vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as exploitation could enable attackers to execute arbitrary commands through the compromised FreeSWITCH process. Organizations should also review their telephony infrastructure for similar buffer overflow patterns in other components and ensure regular security assessments of telecommunications platforms to identify and remediate similar vulnerabilities before they can be exploited.