CVE-2021-39665 in Android
Summary
by MITRE • 02/11/2022
In checkSpsUpdated of AAVCAssembler.cpp, there is a possible out of bounds read due to a heap buffer overflow. This could lead to remote information disclosure with no additional execution privileges needed. User interaction is needed for exploitation.Product: AndroidVersions: Android-12Android ID: A-204077881
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Analysis
by VulDB Data Team • 02/16/2022
The vulnerability identified as CVE-2021-39665 resides within the AAVCAssembler.cpp component of Android's media processing framework, specifically in the checkSpsUpdated function. This flaw represents a classic heap buffer overflow condition that manifests as an out-of-bounds read operation, making it particularly dangerous for remote exploitation scenarios. The vulnerability affects Android 12 systems and is catalogued under Android ID A-204077881, indicating its severity and the need for immediate attention from security teams.
The technical implementation of this vulnerability stems from inadequate bounds checking within the video stream processing logic. When the system processes specific media data structures, particularly those related to SPS (Sequence Parameter Set) updates in AVC (Advanced Video Coding) streams, the checkSpsUpdated function fails to properly validate array indices or buffer boundaries before accessing heap-allocated memory regions. This allows an attacker to craft malicious media content that triggers memory access violations, potentially leading to information disclosure through memory corruption. The vulnerability is classified under CWE-125 as an out-of-bounds read, which directly aligns with the observed behavior of accessing memory beyond allocated buffer limits.
From an operational perspective, this vulnerability creates a significant risk for remote information disclosure attacks as it requires no additional execution privileges beyond the ability to send specially crafted media content to a target device. The necessity for user interaction suggests that exploitation typically occurs through media playback scenarios such as email attachments, web browsing, or messaging applications that process multimedia content. This characteristic places the vulnerability in the ATT&CK framework under the T1059.007 technique for command and control communications, as successful exploitation could enable attackers to extract sensitive information from memory locations that should remain protected. The remote nature of the attack vector means that adversaries can potentially exploit this vulnerability without physical access to devices, making it particularly concerning for enterprise environments and mobile device management systems.
The mitigation strategies for CVE-2021-39665 should prioritize the immediate deployment of Android security patches provided by Google, which address the underlying buffer overflow condition through proper bounds checking and memory validation. Organizations should also implement network-based filtering measures to block suspicious media content, particularly when dealing with untrusted sources. Security teams should monitor for potential exploitation attempts through network traffic analysis, focusing on unusual media processing patterns that might indicate exploitation attempts. Additionally, regular security assessments of media processing components within mobile applications and web browsers should be conducted to identify similar vulnerabilities. The implementation of runtime protections such as address space layout randomization and stack canaries can provide additional defense-in-depth measures, though these are secondary to the primary patching approach. System administrators should also consider implementing mobile device management policies that enforce automatic security updates to ensure all devices receive the necessary protections against this and similar vulnerabilities.