CVE-2013-2596 in Android
Summary
by MITRE
Integer overflow in the fb_mmap function in drivers/video/fbmem.c in the Linux kernel before 3.8.9, as used in a certain Motorola build of Android 4.1.2 and other products, allows local users to create a read-write memory mapping for the entirety of kernel memory, and consequently gain privileges, via crafted /dev/graphics/fb0 mmap2 system calls, as demonstrated by the Motochopper pwn program.
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Analysis
by VulDB Data Team • 04/22/2026
The vulnerability described in CVE-2013-2596 represents a critical integer overflow flaw within the Linux kernel's framebuffer memory mapping functionality. This issue resides in the fb_mmap function located in drivers/video/fbmem.c, affecting kernel versions prior to 3.8.9 and specifically impacting certain Motorola Android builds including version 4.1.2. The vulnerability stems from inadequate input validation and arithmetic handling within the memory mapping subsystem, creating a pathway for privilege escalation through malformed system calls.
The technical exploitation of this vulnerability occurs through crafted /dev/graphics/fb0 mmap2 system calls that manipulate the framebuffer memory mapping process. When a local user executes these specially crafted operations, the integer overflow in the fb_mmap function causes the kernel to incorrectly calculate memory mapping boundaries. This miscalculation results in a read-write memory mapping that encompasses the entire kernel memory space rather than the intended limited framebuffer region. The flaw leverages the absence of proper bounds checking when processing memory mapping parameters, allowing attackers to bypass normal memory protection mechanisms that typically isolate user-space processes from kernel-space memory.
The operational impact of this vulnerability is severe and far-reaching within the affected systems. Local users who can access the framebuffer device can leverage this flaw to gain complete control over kernel memory, enabling them to read and modify any kernel data structures, function pointers, or sensitive information. This privilege escalation capability allows attackers to execute arbitrary code with kernel-level privileges, effectively compromising the entire system security posture. The vulnerability is particularly dangerous in mobile environments where Android devices rely heavily on framebuffer operations for graphics rendering and display management, making it a prime target for exploitation in mobile malware and rootkit development.
The exploitation technique demonstrated by the Motochopper pwn program illustrates how this vulnerability can be weaponized in practice. This proof-of-concept shows that attackers can construct specific memory mapping requests that trigger the integer overflow condition, creating a mapping that spans kernel memory addresses. The vulnerability directly relates to CWE-190, which addresses integer overflow conditions, and maps to ATT&CK technique T1068, which covers "Local Privilege Escalation" through kernel exploits. The flaw also connects to broader categories of memory corruption vulnerabilities that affect system stability and security boundaries, particularly in device driver components where memory management is critical.
Mitigation strategies for CVE-2013-2596 primarily involve applying the official kernel patches released with version 3.8.9 and subsequent updates. System administrators should ensure all affected devices receive timely security updates, particularly in enterprise environments where mobile devices may be running outdated Android versions. Additional protective measures include implementing proper access controls to framebuffer devices, restricting local user privileges where possible, and monitoring for unusual memory mapping activity. Organizations should also conduct vulnerability assessments to identify systems running affected kernel versions and implement network segmentation to limit potential exploitation vectors. The fix addresses the underlying integer overflow by introducing proper bounds checking and input validation in the memory mapping calculations, ensuring that memory regions cannot be incorrectly expanded beyond their intended boundaries.