CVE-2009-5029 in C Library
Summary
by MITRE
Integer overflow in the __tzfile_read function in glibc before 2.15 allows context-dependent attackers to cause a denial of service (crash) and possibly execute arbitrary code via a crafted timezone (TZ) file, as demonstrated using vsftpd.
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Analysis
by VulDB Data Team • 12/04/2024
The vulnerability identified as CVE-2009-5029 represents a critical integer overflow flaw within the glibc library's __tzfile_read function, affecting versions prior to 2.15. This issue manifests when processing timezone files and creates a pathway for attackers to manipulate system behavior through carefully crafted malicious timezone data. The vulnerability operates within the broader context of system time management and localization services that are fundamental to operating system functionality. When a system processes an improperly formatted timezone file, the integer overflow can cause unpredictable behavior in the underlying time zone parsing mechanism, potentially leading to system instability and service disruption. The flaw specifically resides in how the system handles integer arithmetic during timezone file parsing operations, where insufficient bounds checking allows for overflow conditions that can corrupt memory structures and execution flow.
The technical exploitation of this vulnerability occurs through manipulation of timezone data files that are processed by the glibc library during system time zone initialization or runtime updates. When the __tzfile_read function encounters a malformed timezone file with oversized or malformed data structures, the integer overflow can result in buffer overflows or memory corruption that may lead to program crashes or more severe consequences. The vulnerability's context-dependent nature means that successful exploitation requires specific conditions to be met, including the ability to influence or replace timezone files that are subsequently processed by the vulnerable glibc version. Attackers can leverage this weakness by crafting malicious timezone files that, when processed by applications or system services, trigger the overflow condition and potentially execute arbitrary code within the context of the vulnerable process.
The operational impact of CVE-2009-5029 extends beyond simple denial of service scenarios to potentially enable remote code execution in certain configurations. Systems running vulnerable versions of glibc that process user-supplied timezone data or that are subject to timezone file manipulation attacks face significant risk of compromise. The demonstrated exploitation using vsftpd illustrates how this vulnerability can be leveraged in real-world scenarios where FTP servers and other network services might be influenced by timezone data manipulation. The vulnerability affects a broad range of applications that depend on glibc for time zone handling, including web servers, network services, and system management tools that process timezone information during normal operation. Organizations with systems that allow untrusted users to influence timezone settings or that automatically download timezone data from external sources are particularly vulnerable to exploitation.
Mitigation strategies for this vulnerability center on upgrading to glibc version 2.15 or later, which contains the necessary patches to address the integer overflow condition in the __tzfile_read function. System administrators should prioritize patching affected systems and verify that timezone data sources are properly validated and secured against malicious manipulation. Additional protective measures include implementing strict access controls on timezone files, monitoring for unauthorized timezone data modifications, and ensuring that applications processing timezone information are running with minimal privileges. Security teams should also consider implementing network segmentation and access controls to limit the potential impact of timezone-based attacks, particularly in environments where multiple services might be exposed to untrusted timezone data sources. The vulnerability aligns with CWE-190, which addresses integer overflow conditions, and represents a classic example of how seemingly benign input processing can lead to critical security consequences. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and execution through system services, highlighting the importance of maintaining secure system libraries and validating all input data sources.