CVE-2020-0496 in Android
Summary
by MITRE • 12/15/2020
In CPDF_RenderStatus::LoadSMask of cpdf_renderstatus.cpp, there is a possible memory corruption due to a use-after free. This could lead to local information disclosure with no additional execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-11Android ID: A-149481220
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Analysis
by VulDB Data Team • 12/18/2020
The vulnerability identified as CVE-2020-0496 resides within the CPDF_RenderStatus::LoadSMask function in the cpdf_renderstatus.cpp file of Android's PDF rendering subsystem. This memory corruption issue stems from a use-after-free condition that occurs when the system attempts to access memory that has already been freed during the processing of PDF documents. The flaw is particularly concerning as it exists within the core PDF rendering engine that handles document processing across Android 11 devices, making it a critical security concern for mobile platforms.
The technical implementation of this vulnerability involves the improper management of memory resources during PDF SMask (soft mask) processing. When a PDF document contains specific SMask elements, the rendering process allocates memory for these graphical components and subsequently frees it. However, the code fails to properly invalidate pointers or check for proper memory state before attempting to access the freed memory region. This use-after-free condition creates an opportunity for memory corruption that can be exploited to extract sensitive information from the system's memory space. The vulnerability is classified under CWE-416 as a Use After Free condition, which represents a well-known class of memory safety issues that have historically led to various security exploits.
From an operational perspective, this vulnerability enables local information disclosure without requiring any special privileges or user interaction for exploitation. The attack vector is particularly dangerous because it can be triggered simply by processing a malicious PDF document, which could be delivered through various means such as email attachments, web downloads, or file sharing applications. The lack of user interaction requirements makes this vulnerability especially concerning for mobile environments where users frequently encounter PDF content from untrusted sources. The memory corruption can potentially expose sensitive data such as cryptographic keys, user credentials, or application memory contents that may be accessible through the corrupted memory regions.
The security implications extend beyond simple information disclosure, as this vulnerability can serve as a stepping stone for more sophisticated attacks. Attackers could potentially leverage the memory corruption to gain insights into memory layout, application state, or even execute arbitrary code in some scenarios. The Android platform's security model relies heavily on proper memory management to prevent such vulnerabilities from escalating into full system compromises. However, the use-after-free condition in the PDF rendering engine represents a significant weakness that can be exploited to bypass security boundaries, particularly when combined with other vulnerabilities or through advanced exploitation techniques.
Mitigation strategies for CVE-2020-0496 should focus on immediate patch deployment through Android security updates, as the vulnerability exists in core system components. Organizations should prioritize updating Android 11 devices to the latest security patches that address this specific memory corruption issue. Additionally, implementing PDF document filtering and sandboxing measures can help reduce the attack surface by preventing processing of potentially malicious PDF content. Network-level controls should be deployed to scan and block suspicious PDF files before they reach end-user devices. The vulnerability highlights the importance of memory safety practices in mobile operating systems and underscores the need for comprehensive code review processes that specifically target memory management issues. Regular security assessments of PDF rendering engines and other core system components should be conducted to identify and remediate similar vulnerabilities before they can be exploited in the wild.