CVE-2018-5851 in Android
Summary
by MITRE
Buffer over flow can occur while processing a HTT_T2H_MSG_TYPE_TX_COMPL_IND message with an out-of-range num_msdus value in all Android releases from CAF (Android for MSM, Firefox OS for MSM, QRD Android) using the Linux Kernel.
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Analysis
by VulDB Data Team • 02/18/2020
This vulnerability represents a critical buffer overflow condition that affects Android devices utilizing Qualcomm chipsets and the Linux kernel. The flaw manifests specifically when processing HTT_T2H_MSG_TYPE_TX_COMPL_IND messages, which are part of the wireless networking stack responsible for handling transmission completion indicators. The vulnerability stems from insufficient input validation where the num_msdus field contains an out-of-range value that exceeds the allocated buffer boundaries. This condition creates a scenario where maliciously crafted wireless packets could trigger memory corruption during the processing of network transmission completions, potentially allowing attackers to execute arbitrary code within the kernel space. The vulnerability impacts all Android releases from CAF including Android for MSM, Firefox OS for MSM, and QRD Android, indicating a widespread exposure across Qualcomm-based devices. According to CWE classification, this represents a classic buffer overflow vulnerability (CWE-121) that occurs due to inadequate bounds checking in memory operations. The attack surface is particularly concerning as it operates at the kernel level where successful exploitation could lead to complete system compromise.
The technical exploitation of this vulnerability requires an attacker to be within range of the target device's wireless network interface and to craft specially formatted wireless packets that contain malicious values in the num_msdus field. This aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as the attacker would need to leverage wireless protocols to deliver the malicious payload. The buffer overflow occurs because the system does not validate that the num_msdus value falls within acceptable parameters before using it to determine buffer allocation or loop iterations. This creates a predictable pattern where the overflow can overwrite adjacent memory locations, potentially corrupting critical kernel data structures or even overwriting function return addresses. The vulnerability's persistence across multiple Android variants suggests that the underlying flaw exists in the Qualcomm driver implementations rather than being specific to individual Android versions, making it particularly dangerous for device manufacturers who may not have updated their kernel implementations.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise and data theft capabilities. Successful exploitation could enable attackers to escalate privileges from user-space to kernel-space, bypassing standard security mechanisms including SELinux and other mandatory access controls. The affected devices would remain vulnerable until patched, creating a persistent threat vector for attackers who maintain knowledge of the specific wireless packet structures. Network-based attacks become feasible since wireless interfaces are typically always active, and the vulnerability does not require physical access to the device. This makes the exploitation particularly attractive to threat actors targeting mobile devices in enterprise environments or public spaces where wireless networks are prevalent. The vulnerability's nature as a kernel-level buffer overflow also means that any data processed through the affected wireless subsystem becomes potentially compromised, including sensitive communications, stored credentials, and personal information. The attack chain would typically involve initial wireless packet delivery followed by successful buffer overflow exploitation, potentially leading to persistent backdoor installation or complete device takeover.
Mitigation strategies for this vulnerability should focus on immediate patch deployment through official Android security updates, as the fix typically involves implementing proper bounds checking for the num_msdus field before processing. Network administrators should consider disabling unnecessary wireless interfaces when not actively in use, and device manufacturers should implement additional input validation layers in their wireless driver implementations. The solution aligns with defensive techniques described in ATT&CK framework under T1566 for credential access and T1070 for indicator removal, as proper input validation serves as both prevention and detection mechanism. Organizations should also implement network monitoring to detect anomalous wireless traffic patterns that might indicate exploitation attempts, particularly focusing on malformed transmission completion messages. Device users should ensure timely installation of security updates and avoid using devices in high-risk environments where wireless-based attacks are prevalent. The vulnerability underscores the importance of secure coding practices in kernel space development, particularly around buffer management and input validation, which should be enforced through automated code review processes and security testing protocols. Regular security assessments of wireless subsystems and kernel components are essential to identify similar vulnerabilities that may exist in other parts of the system architecture.