CVE-2017-9719 in Android
Summary
by MITRE
In android for MSM, Firefox OS for MSM, QRD Android, with all Android releases from CAF using the Linux kernel, in the kernel driver MDSS, a buffer overflow can occur in HDMI CEC parsing if frame size is out of range.
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Analysis
by VulDB Data Team • 12/07/2019
The vulnerability identified as CVE-2017-9719 represents a critical buffer overflow condition within the Linux kernel driver MDSS (Mobile Display Subsystem) found in various Android implementations including those from Qualcomm Automotive Framework and Firefox OS for MSM platforms. This flaw specifically manifests during HDMI CEC (Consumer Electronics Control) frame parsing operations when the system encounters frame sizes that exceed expected parameters, creating an exploitable condition that could allow malicious actors to manipulate kernel memory structures.
The technical implementation of this vulnerability resides within the MDSS kernel driver where HDMI CEC communication is processed through the Linux kernel subsystem. When an HDMI CEC frame is received with an invalid or unexpectedly large frame size parameter, the kernel driver fails to properly validate this input before attempting to copy or process the frame data into a predetermined buffer space. This lack of proper bounds checking creates a classic buffer overflow scenario where maliciously crafted HDMI CEC frames can overwrite adjacent memory locations, potentially leading to arbitrary code execution within kernel space. The vulnerability is particularly concerning as it operates at the kernel level where such exploits can result in complete system compromise.
The operational impact of CVE-2017-9719 extends beyond simple denial of service conditions to encompass full system exploitation capabilities. An attacker who can inject malicious HDMI CEC frames could potentially execute arbitrary code with kernel privileges, allowing for privilege escalation, persistent backdoor installation, and complete device takeover. This vulnerability affects all Android releases from CAF that utilize the Linux kernel, making it widespread across numerous mobile devices and embedded systems. The attack surface is particularly relevant in environments where HDMI CEC communication is enabled and untrusted external devices may be connected, as this communication channel could be exploited without requiring physical access to the device.
This vulnerability aligns with CWE-121, which describes the classic stack-based buffer overflow condition, and represents a clear violation of secure coding practices regarding input validation and bounds checking. From an ATT&CK framework perspective, this vulnerability maps to T1068, which involves exploiting legitimate credentials and system access, and potentially T1059, which covers command and scripting interpreter usage. The mitigation strategies should include immediate kernel updates from device manufacturers, implementation of input validation controls within the MDSS driver, and potential disabling of HDMI CEC functionality when not required. Additionally, system administrators should consider network segmentation to limit potential attack vectors and implement monitoring for unusual HDMI CEC communication patterns that might indicate exploitation attempts.