CVE-2021-39680 in Android
Summary
by MITRE • 01/14/2022
In sec_SHA256_Transform of sha256_core.c, there is a possible way to read heap data due to uninitialized data. 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-197965864References: N/A
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Analysis
by VulDB Data Team • 01/19/2022
The vulnerability identified as CVE-2021-39680 represents a critical information disclosure flaw within the Android kernel's cryptographic implementation, specifically within the SHA-256 hash function core. This issue manifests in the sec_SHA256_Transform function located in the sha256_core.c source file, where uninitialized memory data can potentially be read during cryptographic operations. The vulnerability stems from improper initialization of memory variables within the hash transformation process, creating a pathway for sensitive heap data to be inadvertently exposed. The flaw is particularly concerning because it operates at the kernel level, requiring system execution privileges for exploitation but not necessitating user interaction, making it a significant threat vector for local attackers with system-level access. The Android ID A-197965864 further contextualizes this vulnerability within the Android security framework, indicating its classification and severity within the Android security ecosystem.
The technical implementation of this vulnerability involves the SHA-256 cryptographic algorithm's core transformation function where memory initialization fails to properly set all data elements before processing. This uninitialized data can contain remnants of previous operations or sensitive information from other memory regions, allowing an attacker with system privileges to potentially extract confidential information from the heap memory. The flaw occurs during the hash computation process where the algorithm processes input data through multiple rounds, and the uninitialized memory values can influence the final hash output or expose underlying data. This type of vulnerability falls under CWE-755 as an improper initialization of data, specifically within cryptographic contexts where memory integrity is paramount for security. The operational impact extends beyond simple information disclosure, as the leaked heap data could contain sensitive cryptographic keys, system credentials, or other confidential information that could be leveraged for further attacks.
The exploitation of this vulnerability requires an attacker to possess system execution privileges, which aligns with the ATT&CK technique T1059.001 for command and scripting interpreter and potentially T1068 for exploit for privilege escalation. The lack of user interaction requirement makes this vulnerability particularly dangerous in environments where system-level access is obtainable through other attack vectors. The information disclosure could expose sensitive data that might include cryptographic material, system configuration details, or other confidential information stored in memory. This vulnerability represents a significant risk to Android devices running affected kernel versions, as it could be exploited to gain insights into the system's internal operations and potentially facilitate more sophisticated attacks. The impact is particularly severe in mobile environments where device security is paramount, and any information leakage could compromise user privacy and system integrity.
Mitigation strategies for CVE-2021-39680 should focus on ensuring proper memory initialization within cryptographic functions and implementing comprehensive code review processes for kernel-level implementations. The recommended approach involves updating to patched kernel versions that properly initialize all memory variables before cryptographic operations, with the fix addressing the uninitialized data issue in the SHA-256 core implementation. System administrators should prioritize applying security patches promptly, particularly in environments where system-level access might be compromised. Additional mitigations include implementing memory sanitization techniques, conducting thorough code audits for similar uninitialized data issues, and establishing robust security testing protocols for cryptographic implementations. The vulnerability highlights the importance of proper memory management in security-critical code sections and underscores the need for adherence to secure coding practices that prevent information disclosure through uninitialized memory access patterns. Organizations should also consider implementing monitoring solutions to detect potential exploitation attempts and maintain updated threat intelligence regarding similar vulnerabilities in cryptographic implementations.