CVE-2023-35693 in Android
Summary
by MITRE • 07/13/2023
In incfs_kill_sb of fs/incfs/vfs.c, there is a possible memory corruption due to a use after free. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation.
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Analysis
by VulDB Data Team • 08/05/2023
The vulnerability identified as CVE-2023-35693 resides within the incfs_kill_sb function located in the fs/incfs/vfs.c file of the Linux kernel, representing a critical use after free condition that can result in memory corruption. This flaw occurs within the filesystem implementation of the incfs (incremental filesystem) subsystem, which is designed to provide incremental file system operations. The vulnerability stems from improper memory management where a pointer is accessed after the memory it references has been freed, creating a scenario where arbitrary code execution can potentially occur through memory corruption. The issue specifically manifests during the destruction of the superblock in the incremental filesystem, where the kernel fails to properly handle reference counting or memory deallocation sequences, leading to dangling pointer access. Such memory corruption vulnerabilities are particularly dangerous because they can be exploited to gain unauthorized access to system resources and potentially escalate privileges to the highest system level.
The technical exploitation of this vulnerability requires an attacker to have system execution privileges and local access to the target system, though no user interaction is necessary for the attack to succeed. The use after free condition falls under the CWE-416 category of Use After Free, which is classified as a critical vulnerability in the Common Weakness Enumeration framework and represents a well-known class of memory safety issues. When the incfs_kill_sb function executes, it attempts to operate on memory that has already been deallocated, potentially allowing an attacker to control the execution flow of the kernel by corrupting memory structures. This memory corruption can manifest in various ways including stack smashing, heap corruption, or even direct code execution depending on the memory layout and the specific conditions under which the vulnerability is triggered. The vulnerability is particularly concerning in kernel space where memory corruption can lead to complete system compromise.
The operational impact of CVE-2023-35693 extends beyond simple privilege escalation as it represents a fundamental breakdown in kernel memory management that can be leveraged for broader system compromise. An attacker with local access can exploit this vulnerability to gain root privileges without requiring user interaction, making it particularly dangerous in multi-user environments or systems where local access is possible. The vulnerability affects systems running Linux kernels that implement the incfs filesystem functionality, which is commonly used in various enterprise and cloud environments for incremental backup and file synchronization operations. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques and specifically relates to T1068 (Local Privilege Escalation) and T1059 (Command and Scripting Interpreter) where the memory corruption can be used to execute arbitrary code with elevated privileges. The lack of user interaction requirement means that once an attacker gains local access, they can automatically exploit this vulnerability without further engagement.
Mitigation strategies for CVE-2023-35693 should focus on immediate kernel updates and patches provided by the Linux kernel maintainers, as this vulnerability is likely to be addressed through proper memory management fixes in the incfs subsystem. Organizations should prioritize patching affected systems and monitoring for exploitation attempts, particularly in environments where local access is possible or where the incfs filesystem is actively used. The recommended approach includes applying the latest security patches from kernel vendors, implementing proper access controls to limit local system access, and monitoring system logs for unusual activities that might indicate exploitation attempts. Additionally, system administrators should consider implementing kernel hardening techniques such as stack canaries, address space layout randomization, and kernel module signing to further reduce the attack surface and make exploitation more difficult. Regular security audits of kernel components and filesystem implementations should also be conducted to identify similar memory management issues that could potentially lead to privilege escalation vulnerabilities in other subsystems.