CVE-2006-6244 in freePBX
Summary
by MITRE
Coalescent Systems freePBX (formerly Asterisk Management Portal) before 2.2.0rc1 allows attackers to execute arbitrary commands via shell metacharacters in (1) CALLERID(name) or (2) CALLERID(number).
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Analysis
by VulDB Data Team • 08/09/2018
The vulnerability identified as CVE-2006-6244 affects Coalescent Systems freePBX platform prior to version 2.2.0rc1, representing a critical command injection flaw that enables remote attackers to execute arbitrary system commands. This vulnerability specifically targets the CALLERID functionality within the Asterisk-based telephony system, where the application fails to properly sanitize user input before incorporating it into system commands. The flaw exists in the handling of caller identification data, which is commonly used in telephony systems to display information about incoming calls. When attackers manipulate the CALLERID(name) or CALLERID(number) parameters through shell metacharacters, they can inject malicious commands that the system processes without adequate validation or escaping mechanisms.
The technical implementation of this vulnerability stems from insufficient input validation and improper output encoding within the freePBX application's telephony handling modules. The system directly incorporates user-supplied caller ID information into shell commands without proper sanitization, creating an environment where operators such as semicolons, ampersands, or backticks can be interpreted by the underlying shell as command separators or execution triggers. This represents a classic command injection vulnerability that aligns with CWE-77, which specifically addresses improper neutralization of special elements used in OS commands. The attack vector operates through the telephony interface where malicious callers can manipulate the caller ID fields to include shell metacharacters that will be executed by the system when processing incoming call data.
The operational impact of this vulnerability extends beyond simple command execution, as it provides attackers with potential full system compromise capabilities. Successful exploitation can enable attackers to gain unauthorized access to the underlying operating system, potentially leading to complete system takeover, data exfiltration, or service disruption. The vulnerability affects telephony infrastructure that relies on freePBX for call management, which could include business phone systems, VoIP gateways, or unified communications platforms. Given that many organizations depend on these systems for critical communications, the potential for service disruption or data breaches is significant. The vulnerability also aligns with ATT&CK technique T1059.001, which covers command and scripting interpreter, specifically focusing on the use of shell commands for malicious purposes.
Mitigation strategies for CVE-2006-6244 require immediate patching of affected freePBX installations to version 2.2.0rc1 or later, which includes proper input sanitization and output escaping mechanisms. Organizations should implement network segmentation to limit access to telephony systems and restrict the privileges of the telephony service accounts. Input validation should be strengthened to reject or escape special shell characters in caller ID fields, while output encoding should ensure that any user-supplied data cannot be interpreted as shell commands. Security monitoring should be enhanced to detect unusual patterns in telephony system logs that might indicate exploitation attempts. Additionally, implementing principle of least privilege for telephony system components and regular security audits of telephony configurations will help reduce the attack surface and prevent similar vulnerabilities from emerging in other parts of the communication infrastructure.