CVE-2021-39647 in Android
Summary
by MITRE • 12/15/2021
In mon_smc_load_sp of gs101-sc/plat/samsung/exynos/soc/exynos9845/smc_booting.S, there is a possible reinitialization of TEE due to improper locking. This could lead to local information disclosure with System execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android kernelAndroid ID: A-198713939References: N/A
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 12/18/2021
The vulnerability identified as CVE-2021-39647 resides within the Samsung Exynos 9845 SoC implementation of the Android kernel, specifically in the mon_smc_load_sp function located in the gs101-sc/plat/samsung/exynos/soc/exynos9845/smc_booting.S file. This flaw represents a critical security weakness that affects the Trusted Execution Environment (TEE) initialization process on Samsung devices. The vulnerability stems from improper locking mechanisms during the TEE reinitialization procedure, creating a race condition that can be exploited to compromise the security boundaries between the normal world and the secure world of the device.
The technical flaw manifests as a lack of proper synchronization primitives when handling the TEE loading process, allowing for potential reinitialization of the Trusted Execution Environment without adequate protection. This improper locking mechanism creates a scenario where concurrent access to the TEE initialization functions could result in unpredictable behavior, potentially exposing sensitive information from the secure environment to the normal world. The vulnerability specifically impacts the Samsung Exynos 9845 SoC platform, which is used in various Samsung Galaxy devices, making it a widespread concern across multiple Android devices. According to the Android ID A-198713939, this issue affects the kernel-level implementation of the Samsung-specific platform support code.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables local attackers with system execution privileges to potentially extract confidential data from the TEE environment. While user interaction is not required for exploitation, the attacker must already possess system-level privileges, which typically means they have root access or equivalent administrative capabilities on the device. This makes the vulnerability particularly dangerous in scenarios where privilege escalation has already occurred, as it can be leveraged to extract sensitive cryptographic keys, user credentials, or other confidential information stored within the secure world. The vulnerability falls under CWE-362, which describes "Concurrent Execution using Shared Resource with Improper Synchronization," and aligns with ATT&CK technique T1059.001 for execution through system commands, potentially enabling further attacks on the device's security architecture.
Mitigation strategies for CVE-2021-39647 should focus on implementing proper locking mechanisms and synchronization primitives within the mon_smc_load_sp function to prevent concurrent access during TEE initialization. Device manufacturers should ensure that all TEE loading operations are properly protected with mutexes or similar synchronization constructs to prevent race conditions. Additionally, kernel updates and patches should be deployed immediately to address this vulnerability, as the issue affects the fundamental security architecture of affected devices. Security researchers and device manufacturers should also consider implementing runtime monitoring for abnormal TEE initialization patterns and conduct thorough code reviews of similar functions across different SoC platforms to identify potential similar vulnerabilities. The patch should include proper validation of TEE state transitions and ensure that reinitialization attempts are properly gated by appropriate locking mechanisms, preventing unauthorized access to secure environment resources during critical initialization phases.