CVE-2009-2191 in Mac OS X
Summary
by MITRE
Format string vulnerability in Login Window in Apple Mac OS X 10.4.11 and 10.5 before 10.5.8 allows attackers to execute arbitrary code or cause a denial of service (application crash) via format string specifiers in an application name.
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Analysis
by VulDB Data Team • 08/13/2021
The vulnerability identified as CVE-2009-2191 represents a critical format string flaw within the Login Window component of Apple Mac OS X operating systems. This issue affects versions 10.4.11 and 10.5 prior to 10.5.8, creating a significant security risk that could be exploited by malicious actors to gain unauthorized system access or disrupt normal operations. The vulnerability specifically resides in how the Login Window processes application names, failing to properly validate or sanitize format string specifiers that may be embedded within these identifiers.
The technical nature of this flaw stems from improper input validation within the login process where application names are directly used in format string functions without adequate sanitization. When an attacker crafts a malicious application name containing format string specifiers such as %x, %s, or %n, the vulnerable code attempts to process these characters as formatting directives rather than literal text. This misinterpretation creates opportunities for memory corruption, stack manipulation, and arbitrary code execution. The vulnerability aligns with CWE-134, which specifically addresses format string vulnerabilities where format strings are constructed from user-supplied data without proper validation. Attackers can leverage this weakness to overwrite critical memory locations, inject malicious code into the login process, or cause application crashes through buffer overflows.
The operational impact of CVE-2009-2191 extends beyond simple denial of service scenarios to encompass full system compromise capabilities. An attacker who successfully exploits this vulnerability could execute arbitrary code with the privileges of the login process, potentially gaining root access to the system. The login window represents a critical system component that runs with elevated privileges, making it an attractive target for attackers seeking persistent system access. Additionally, the vulnerability can be exploited to cause application crashes that may lead to denial of service conditions, preventing legitimate users from accessing their systems. This type of exploitation aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation' and demonstrates how format string vulnerabilities can be leveraged for elevation of privileges.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected systems to the latest supported versions of Mac OS X. Apple released security updates addressing this issue in Mac OS X 10.5.8 and later versions, making it essential for administrators to apply these patches promptly. System administrators should also implement network monitoring to detect potential exploitation attempts through malformed application names or unusual login patterns. Additional protective measures include restricting the ability to load custom applications during the login process and implementing proper input validation mechanisms that prevent format string specifiers from being processed as literal text. The vulnerability underscores the importance of secure coding practices and proper input sanitization, particularly in system components that handle user-provided data. Organizations should also consider implementing privilege separation techniques and regular security assessments to identify similar vulnerabilities in their operating systems and applications.