CVE-2007-2835 in unicon-imc2
Summary
by MITRE
Multiple stack-based buffer overflows in (1) CCE_pinyin.c and (2) xl_pinyin.c in ImmModules/cce/ in unicon-imc2 3.0.4, as used by zhcon and other applications, allow local users to gain privileges via a long HOME environment variable.
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Analysis
by VulDB Data Team • 07/21/2019
The vulnerability described in CVE-2007-2835 represents a critical stack-based buffer overflow condition affecting the unicon-imc2 3.0.4 input method component. This flaw exists within two specific source files CCE_pinyin.c and xl_pinyin.c located in the ImmModules/cce/ directory structure. The vulnerability manifests when applications utilizing this input method library process a specially crafted HOME environment variable that exceeds the allocated buffer size. This particular implementation flaw demonstrates poor memory management practices where input validation is insufficient to prevent buffer overrun conditions that can lead to arbitrary code execution.
The technical implementation of this vulnerability stems from the lack of proper bounds checking in the string handling functions within the pinyin input modules. When the system processes user input through the HOME environment variable, the code fails to validate the length of the input against the fixed buffer size allocated for processing. This creates a classic stack-based buffer overflow scenario where additional data written beyond the buffer boundaries can overwrite adjacent memory locations including return addresses, function pointers, and other critical control data. The vulnerability is classified as local privilege escalation since it requires a user to execute the vulnerable application with elevated privileges to effectively exploit the condition.
From an operational perspective, this vulnerability poses significant security risks to systems utilizing zhcon or other applications that depend on the unicon-imc2 input method library. The local user can leverage this condition to execute arbitrary code with the privileges of the target application, potentially leading to complete system compromise. The attack vector is particularly concerning as it requires minimal user interaction beyond setting an environment variable, making it an attractive target for privilege escalation attacks. This vulnerability directly aligns with CWE-121 Stack-based Buffer Overflow and CWE-787 Out-of-bounds Write, representing fundamental memory safety issues that violate secure coding practices.
The exploitation of this vulnerability can be mapped to several ATT&CK tactics including privilege escalation and execution. Specifically, it enables an attacker to perform local privilege escalation by leveraging the buffer overflow to execute malicious code with elevated privileges. The vulnerability also relates to the technique of environment variable manipulation as the attack relies on controlling the HOME environment variable to trigger the overflow condition. Additionally, this flaw demonstrates poor input validation practices that align with ATT&CK technique T1059 Command and Scripting Interpreter, where attackers can manipulate system behavior through controlled inputs that bypass normal validation mechanisms. Organizations should implement immediate mitigation strategies including updating to patched versions of the unicon-imc2 library, implementing proper input validation, and monitoring for suspicious environment variable usage patterns.