CVE-2021-0488 in Android
Summary
by MITRE • 04/15/2021
In pb_write of pb_encode.c, there is a possible out of bounds write due to a missing bounds check. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android kernelAndroid ID: A-178754781
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Analysis
by VulDB Data Team • 04/21/2021
The vulnerability identified as CVE-2021-0488 resides within the protobuf-c library implementation in Android's kernel components, specifically within the pb_write function located in pb_encode.c. This issue represents a classic out-of-bounds write vulnerability that occurs when the system fails to properly validate buffer boundaries before performing write operations. The flaw manifests during protobuf message encoding processes where the library attempts to write data to memory locations beyond the allocated buffer space, creating a potential attack surface for privilege escalation exploits.
The technical root cause of this vulnerability stems from inadequate bounds checking within the protobuf encoding mechanism. When processing serialized data structures, the pb_write function does not sufficiently validate the length of data being written against the available buffer capacity, allowing for potential memory corruption. This type of vulnerability falls under the CWE-121 category of stack-based buffer overflow, though in this kernel context it manifests as a more generalized out-of-bounds write condition. The vulnerability's presence in the Android kernel components means that exploitation could occur through kernel-level processes that utilize protobuf encoding for communication protocols or data serialization.
The operational impact of CVE-2021-0488 extends to local privilege escalation scenarios where an attacker with system execution privileges could leverage this vulnerability to gain elevated access to the Android kernel. While the vulnerability does not require user interaction for exploitation, it necessitates that the attacker already possess system execution capabilities, making it particularly dangerous in environments where such privileges are already compromised. The implications for Android security are significant as this vulnerability could potentially allow attackers to execute arbitrary code with kernel-level privileges, effectively bypassing standard Android security boundaries and access controls. The exploitation of this vulnerability aligns with ATT&CK technique T1068 which describes local privilege escalation through kernel exploits, and could contribute to broader attack chains targeting Android device security.
Mitigation strategies for CVE-2021-0488 should focus on immediate patch deployment from Android security updates, as the vulnerability requires kernel-level fixes to properly validate buffer boundaries in the protobuf encoding implementation. System administrators should prioritize applying the latest Android security patches that address this specific bounds checking flaw in pb_encode.c. Additionally, runtime protections such as stack canaries, address space layout randomization, and kernel address space layout randomization should be enabled to make exploitation more difficult. Monitoring for anomalous kernel memory access patterns and implementing proper input validation controls for protobuf data processing can also serve as defensive measures. The vulnerability's classification as a kernel-level issue means that traditional application-level mitigations may be insufficient, requiring comprehensive system-level security hardening approaches that address the underlying buffer management flaws in the protobuf implementation.