CVE-2016-0823 in Android
Summary
by MITRE
The pagemap_open function in fs/proc/task_mmu.c in the Linux kernel before 3.19.3, as used in Android 6.0.1 before 2016-03-01, allows local users to obtain sensitive physical-address information by reading a pagemap file, aka Android internal bug 25739721.
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Analysis
by VulDB Data Team • 07/10/2022
The vulnerability identified as CVE-2016-0823 resides within the Linux kernel's memory management subsystem, specifically in the pagemap_open function located in fs/proc/task_mmu.c. This flaw affects Linux kernel versions prior to 3.19.3 and was particularly significant in Android 6.0.1 systems before the 2016-03-01 security patch release. The issue represents a classic information disclosure vulnerability that undermines the fundamental security principle of memory isolation by exposing sensitive physical address information to unauthorized local processes. The vulnerability manifests through the /proc/pid/pagemap interface which is designed to provide memory mapping information for processes but inadvertently leaks physical memory addresses when accessed by local users.
The technical implementation of this vulnerability stems from insufficient access controls and validation within the pagemap_open function. When a local user process attempts to read the pagemap file associated with a target process, the function fails to properly verify whether the requesting process has appropriate privileges to access the underlying physical memory addresses. This design flaw allows malicious local users to enumerate physical memory mappings and extract information about memory layout, which can be leveraged to bypass various security mechanisms including address space layout randomization. The vulnerability operates at the kernel level and requires local access, making it a local privilege escalation vector that can be exploited by any user with access to the system.
The operational impact of CVE-2016-0823 extends beyond simple information disclosure, as physical address information can be used to construct more sophisticated attacks. Attackers can utilize the leaked memory addresses to perform targeted memory corruption attacks, bypass kernel ASLR protections, or facilitate other exploitation techniques that rely on knowing the physical layout of memory regions. This vulnerability is particularly concerning in mobile environments like Android 6.0.1 where the kernel is already under significant attack surface pressure from various application-level exploits. The exposure of physical addresses can also aid in crafting more precise and effective kernel exploits, as attackers can directly target specific memory locations rather than relying on brute force or educated guessing approaches. This vulnerability aligns with CWE-200 (Information Exposure) and can be categorized under ATT&CK technique T1059.001 (Command and Scripting Interpreter: PowerShell) through the use of command-line tools to access and analyze the exposed information.
Mitigation strategies for CVE-2016-0823 primarily involve applying the official kernel patches released by the Linux kernel development team as part of the 3.19.3 release. System administrators should prioritize updating Android 6.0.1 devices to versions released after 2016-03-01, which contain the necessary security fixes. The patch addresses the vulnerability by implementing proper access controls within the pagemap_open function, ensuring that only processes with appropriate privileges can access physical address information. Additionally, organizations should consider implementing additional security measures such as restricting access to /proc filesystem entries, monitoring for unusual access patterns to pagemap files, and maintaining up-to-date security configurations. The fix demonstrates proper kernel security design principles by enforcing mandatory access controls and preventing unauthorized information disclosure through kernel interfaces. Security monitoring should include detection of attempts to access pagemap files, as this can serve as an indicator of potential exploitation attempts.