CVE-2021-39804 in Android
Summary
by MITRE • 04/12/2022
In reinit of HeifDecoderImpl.cpp, there is a possible crash due to a missing null check. This could lead to remote persistent denial of service in the file picker with no additional execution privileges needed. User interaction is needed for exploitation.Product: AndroidVersions: Android-11 Android-12 Android-12LAndroid ID: A-215002587
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Analysis
by VulDB Data Team • 04/18/2022
The vulnerability described in CVE-2021-39804 resides within the HeifDecoderImpl.cpp component of Android's image decoding infrastructure, specifically during the reinitialization phase of HEIF (High Efficiency Image Format) decoding operations. This flaw represents a classic null pointer dereference issue that can occur when the system attempts to reset or reinitialize the HEIF decoder without properly validating whether certain critical pointers remain valid. The vulnerability is classified under CWE-476 which specifically addresses null pointer dereference conditions that can lead to application crashes and system instability. The affected Android versions include Android 11, 12, and 12L, indicating this is a widespread issue affecting multiple generations of the Android operating system.
The technical execution of this vulnerability requires a specific sequence of operations involving file picker interactions where a malicious HEIF file could trigger the problematic code path during decoder reinitialization. The attack vector is particularly concerning because it requires only user interaction to exploit, meaning an attacker could deliver a malicious HEIF file through various channels such as email attachments, messaging applications, or web downloads. When a user opens the file picker and selects the malicious HEIF file, the system attempts to reinitialize the decoder without proper null validation, leading to an immediate crash of the affected application or potentially the entire system. This scenario aligns with ATT&CK technique T1203 which involves exploiting weaknesses in software to cause system instability or crashes.
The operational impact of this vulnerability extends beyond simple application crashes, as it can be leveraged to achieve persistent denial of service attacks against the file picker functionality and potentially other applications that rely on HEIF decoding capabilities. The lack of additional execution privileges required for exploitation makes this vulnerability particularly dangerous in mobile environments where users frequently interact with file systems and media applications. The vulnerability's classification as a remote persistent denial of service means that an attacker could repeatedly trigger the crash condition, effectively rendering the file picker unusable and disrupting normal user operations. This type of vulnerability can be especially problematic in enterprise environments where mobile device management policies rely on consistent file handling capabilities. The issue demonstrates the importance of proper null pointer validation in memory management and highlights how seemingly minor code path issues can result in significant system stability problems. Organizations should prioritize patching this vulnerability across all affected Android versions to prevent potential exploitation scenarios that could lead to service disruption and user productivity loss.