CVE-2007-6429 in MIT-SHM
Summary
by MITRE
Multiple integer overflows in X.Org Xserver before 1.4.1 allow context-dependent attackers to execute arbitrary code via (1) a GetVisualInfo request containing a 32-bit value that is improperly used to calculate an amount of memory for allocation by the EVI extension, or (2) a request containing values related to pixmap size that are improperly used in management of shared memory by the MIT-SHM extension.
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Analysis
by VulDB Data Team • 08/04/2019
The vulnerability identified as CVE-2007-6429 represents a critical security flaw in the X.Org Xserver version 1.4.1 and earlier, affecting the core graphics subsystem of Unix-like operating systems. This vulnerability stems from improper handling of integer values during memory allocation calculations within two distinct extensions of the X Window System. The flaw exists in the EVI (Extended Video Information) extension and the MIT-SHM (MIT Shared Memory) extension, both of which are integral components of the X server architecture that manage video information and shared memory operations respectively. These extensions are responsible for facilitating efficient graphics processing and memory management between the X server and client applications, making them prime targets for exploitation by malicious actors seeking to compromise system integrity.
The technical implementation of this vulnerability manifests through two distinct attack vectors that exploit integer overflow conditions during memory allocation processes. In the first scenario, the GetVisualInfo request within the EVI extension accepts a 32-bit value that, when improperly converted and used for memory allocation calculations, can cause the system to allocate insufficient memory space. This occurs when the system performs arithmetic operations on the input value without proper bounds checking, resulting in an integer overflow that leads to memory corruption. The second vector involves pixmap size parameters within the MIT-SHM extension where shared memory management calculations use improperly validated values, again leading to memory allocation errors that can be exploited to overwrite critical memory locations. Both scenarios demonstrate a fundamental failure in input validation and integer arithmetic handling within the X server's extension modules, creating conditions where attackers can manipulate memory allocation parameters to achieve arbitrary code execution.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it allows context-dependent attackers to execute arbitrary code with the privileges of the X server process, typically running with elevated system permissions. This presents a significant risk to desktop environments and server systems that rely on X Window System for graphical user interfaces, as successful exploitation could lead to complete system compromise. Attackers can leverage these vulnerabilities by crafting specially crafted X protocol requests that trigger the integer overflow conditions during memory allocation, potentially leading to buffer overflows, memory corruption, or other exploitable conditions that enable code execution. The context-dependent nature of the attack means that exploitation requires specific conditions such as network access to the X server or local access to a system running vulnerable X server software, but once triggered, the consequences can be severe.
Mitigation strategies for CVE-2007-6429 focus primarily on updating to patched versions of the X.Org Xserver, specifically version 1.4.1 or later, where the integer overflow conditions have been addressed through proper bounds checking and input validation. System administrators should also implement network segmentation and access controls to limit exposure of X server instances to untrusted networks, particularly when X11 forwarding is enabled. Additional defensive measures include disabling unnecessary X server extensions, implementing proper firewall rules to restrict X server access, and monitoring for anomalous X protocol traffic patterns that might indicate exploitation attempts. From a compliance perspective, this vulnerability aligns with CWE-190, which addresses integer overflow and underflow conditions, and represents a classic example of how improper input validation can lead to memory corruption vulnerabilities. The attack vectors associated with this vulnerability map to multiple ATT&CK techniques including privilege escalation through code injection and execution of malicious code within legitimate processes, making it a significant concern for organizations maintaining desktop and server environments that rely on X Window System functionality.