CVE-2016-6916 in Video Driver
Summary
by MITRE
Integer overflow in nvhost_job.c in the NVIDIA video driver for Android, Shield TV before OTA 3.3, Shield Table before OTA 4.4, and Shield Table TK1 before OTA 1.5 allows local users to cause a denial of service (system crash) via unspecified vectors, which triggers a buffer overflow.
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Analysis
by VulDB Data Team • 04/25/2017
The vulnerability identified as CVE-2016-6916 represents a critical integer overflow flaw within the NVIDIA video driver component nvhost_job.c that affects various Android-based devices including the Shield TV and Shield Tablet platforms. This issue stems from improper handling of integer arithmetic operations that can lead to unexpected behavior when processing user-supplied data. The vulnerability specifically manifests in the context of local privilege escalation scenarios where an unprivileged user process can manipulate the driver's internal state through carefully crafted inputs. The flaw exists in the kernel-level video driver component that manages job submission and processing for graphics operations, making it particularly dangerous as it operates with elevated privileges and can directly impact system stability.
The technical implementation of this vulnerability involves an integer overflow condition that occurs during buffer size calculations within the job submission mechanism. When processing graphics job requests, the driver performs arithmetic operations to determine buffer allocation sizes, but fails to properly validate or check for overflow conditions. This allows an attacker to submit malicious job parameters that, when processed, result in an integer overflow that subsequently triggers a buffer overflow condition. The underlying cause aligns with CWE-190, which specifically addresses integer overflow and underflow vulnerabilities, and represents a classic example of improper integer handling in kernel space code. The vulnerability can be exploited through local user processes that have access to the graphics driver interface, making it particularly concerning for mobile and embedded systems where user access to such interfaces may be more prevalent.
The operational impact of this vulnerability extends beyond simple denial of service to potentially compromising the entire system stability and integrity. When the integer overflow occurs, it results in a buffer overflow condition that can corrupt adjacent memory locations, leading to unpredictable system behavior including kernel panics, system crashes, and complete system lockups. This type of vulnerability can be particularly problematic in embedded systems and mobile devices where automatic recovery mechanisms may not be sufficient to restore normal operation. The attack vector requires local access to the system, which means that while the vulnerability itself may not be remotely exploitable, it can be leveraged by malicious applications or compromised user accounts to cause system-wide disruptions. The impact on device availability and user experience can be severe, particularly for devices that rely heavily on graphics processing for normal operation.
Mitigation strategies for CVE-2016-6916 should focus on both immediate patching and architectural improvements to prevent similar vulnerabilities. The primary solution involves applying the official NVIDIA driver updates that address the integer overflow condition in nvhost_job.c by implementing proper bounds checking and overflow detection mechanisms. System administrators should prioritize updating all affected devices to OTA versions that include the security patches, particularly for Shield TV and Shield Tablet models that were identified as vulnerable. Additionally, implementing runtime protections such as stack canaries, address space layout randomization, and kernel address space layout randomization can provide additional layers of defense against exploitation attempts. From a defensive perspective, this vulnerability highlights the importance of secure coding practices in kernel space drivers and aligns with ATT&CK technique T1068 which covers local privilege escalation through kernel exploits. Organizations should also consider implementing monitoring solutions to detect unusual graphics driver behavior that might indicate exploitation attempts, and maintain regular security assessments of embedded system components to identify similar integer overflow vulnerabilities in other driver components.