CVE-2016-7913 in Android
Summary
by MITRE
The xc2028_set_config function in drivers/media/tuners/tuner-xc2028.c in the Linux kernel before 4.6 allows local users to gain privileges or cause a denial of service (use-after-free) via vectors involving omission of the firmware name from a certain data structure.
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Analysis
by VulDB Data Team • 09/30/2022
The vulnerability identified as CVE-2016-7913 represents a critical use-after-free flaw in the Linux kernel's tuner driver subsystem, specifically within the xc2028_set_config function located in drivers/media/tuners/tuner-xc2028.c. This issue affects Linux kernel versions prior to 4.6 and stems from improper handling of firmware name data structures during tuner configuration operations. The vulnerability manifests when the firmware name is omitted from a specific data structure, creating a scenario where memory that has been freed is subsequently accessed or modified, leading to unpredictable system behavior and potential privilege escalation.
The technical exploitation of this vulnerability occurs through manipulation of the tuner configuration process where the xc2028_set_config function fails to properly validate or initialize the firmware name field within its data structures. When a firmware name is omitted, the function proceeds with operations on a freed memory reference, creating conditions for memory corruption that can be leveraged by local attackers. This use-after-free condition falls under CWE-416, which specifically addresses the use of memory after it has been freed, and represents a classic vulnerability pattern that can lead to arbitrary code execution or system crashes. The flaw is particularly dangerous because it operates within kernel space, where successful exploitation can result in full system compromise and privilege escalation from unprivileged user accounts to root privileges.
From an operational perspective, this vulnerability poses significant risks to systems utilizing Linux-based television tuner hardware, particularly those running kernel versions before 4.6. The local nature of the attack means that any user with access to the system can potentially exploit this flaw, making it particularly concerning for multi-user environments or systems where untrusted users might have login access. The impact extends beyond simple privilege escalation to include potential denial of service conditions, where the use-after-free scenario can cause kernel panics or system crashes that render the affected system unusable. This vulnerability directly aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation', and represents a classic example of how kernel-level flaws can be exploited to gain elevated system privileges.
Mitigation strategies for CVE-2016-7913 primarily focus on kernel version upgrades to 4.6 or later, where the vulnerability has been addressed through proper memory management and validation of firmware name fields. System administrators should prioritize patching affected systems, particularly those running older kernel versions or embedded systems that may not receive automatic updates. Additionally, implementing proper access controls and limiting user privileges can reduce the attack surface, while monitoring for unusual system behavior or kernel crashes can help detect exploitation attempts. The fix implemented in kernel 4.6 specifically addresses the improper memory handling by ensuring that firmware name validation occurs before any memory operations, preventing the use-after-free condition from occurring in the first place. Organizations should also consider deploying kernel hardening techniques and maintaining up-to-date security patches to protect against similar vulnerabilities in other kernel subsystems.