CVE-2018-12786 in Acrobat Reader
Summary
by MITRE
Adobe Acrobat and Reader 2018.011.20040 and earlier, 2017.011.30080 and earlier, and 2015.006.30418 and earlier versions have an Out-of-bounds read vulnerability. Successful exploitation could lead to information disclosure.
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Analysis
by VulDB Data Team • 08/12/2024
Adobe Acrobat and Reader applications contain a critical out-of-bounds read vulnerability that affects multiple version ranges including 2018.011.20040 and earlier, 2017.011.30080 and earlier, and 2015.006.30418 and earlier. This vulnerability falls under the CWE-129 weakness category, specifically representing an out-of-bounds read condition where the application fails to properly validate array indices before accessing memory locations. The flaw occurs when processing maliciously crafted PDF files that contain malformed data structures, particularly within the document parsing routines that handle various object types and their associated metadata. When the vulnerable software attempts to read data from memory locations beyond the allocated buffer boundaries, it may access uninitialized memory regions or data belonging to other processes, potentially exposing sensitive information. The exploitation of this vulnerability requires an attacker to craft a specially formatted PDF file that triggers the faulty code path during document rendering or parsing operations. This type of vulnerability aligns with ATT&CK technique T1059.007 for execution through script-based languages and T1566 for initial access via malicious documents. The information disclosure impact can be severe as the out-of-bounds read may reveal memory contents including encryption keys, user credentials, system information, or other sensitive data that could be leveraged for further attacks. The vulnerability demonstrates a classic buffer over-read issue where input validation is insufficient to prevent access to memory beyond intended boundaries, making it particularly dangerous in environments where users frequently open PDF documents from untrusted sources. The affected versions represent multiple product releases spanning several years, indicating a persistent flaw in the document processing engine that was not adequately addressed through previous security updates. Organizations using these vulnerable versions face significant risk as the vulnerability can be exploited remotely through web-based attacks, email attachments, or file sharing platforms where malicious PDF files might be encountered. The technical nature of this vulnerability makes it particularly challenging to detect and prevent through traditional network security measures, as the malicious payload appears legitimate until the specific parsing routine is triggered during document processing.
The exploitation of CVE-2018-12786 requires careful crafting of PDF files that can trigger the specific code path leading to the out-of-bounds read condition. Attackers typically leverage this vulnerability by embedding malformed data structures within PDF documents that cause the Acrobat or Reader application to attempt reading beyond the allocated memory space. The vulnerability can be triggered during normal document operations such as opening, rendering, or even printing of malicious files, making it particularly dangerous in enterprise environments where users regularly interact with PDF documents from various sources. When the application encounters the malformed data, it performs an array index check that fails to properly validate the boundary conditions, allowing execution to proceed to memory locations that contain sensitive data. This type of vulnerability is classified as a memory safety issue and represents a common class of bugs that occur in C/C++ applications where developers must manually manage memory allocation and deallocation. The information disclosure aspect of this vulnerability can reveal portions of the application's memory space, potentially exposing cryptographic keys used for document encryption, user session data, or other confidential information. Security researchers have identified that this vulnerability can be exploited through various attack vectors including web-based delivery, phishing campaigns, or malicious file sharing, making it a significant concern for organizations that rely heavily on PDF document processing. The vulnerability's persistence across multiple versions suggests that the underlying code patterns responsible for the flaw were not adequately addressed through patching efforts, indicating a systemic issue in the application's memory handling routines. Organizations should prioritize updating to patched versions of Adobe Acrobat and Reader as soon as possible to mitigate the risk of exploitation, as the vulnerability provides attackers with a direct method for information disclosure without requiring elevated privileges or complex attack chains. The remediation process involves applying the official security patches released by Adobe, which typically include enhanced input validation and memory boundary checking mechanisms to prevent the out-of-bounds read condition from occurring during PDF processing operations.
Adobe's response to this vulnerability included the release of security patches that addressed the memory validation issues within the document parsing components. The patches typically involve implementing additional boundary checks before array access operations, ensuring that all memory accesses are validated against the allocated buffer sizes. This approach aligns with secure coding practices recommended by organizations such as the CERT/CC and the Open Web Application Security Project, which emphasize the importance of input validation and boundary checking in preventing memory safety vulnerabilities. The vulnerability demonstrates the importance of proper software testing, including fuzzing and memory analysis tools that can identify out-of-bounds access conditions before they can be exploited in the wild. Organizations should also implement additional security controls such as email filtering, web application firewalls, and user education programs to reduce the likelihood of encountering malicious PDF files. The vulnerability's classification as an information disclosure issue means that organizations should also consider implementing monitoring and detection capabilities to identify potential exploitation attempts, particularly in environments where PDF processing is frequent. From an operational perspective, this vulnerability highlights the need for regular security updates and patch management processes, as the affected versions span multiple major releases, indicating that the flaw was not properly addressed through previous update cycles. The security community has classified this vulnerability as high-risk due to its potential for information disclosure and the ease with which it can be exploited through common attack vectors such as email attachments or web-based delivery methods. The remediation efforts should also include comprehensive testing of patched versions to ensure that the security updates do not introduce regressions or compatibility issues with existing document processing workflows. Organizations should also consider implementing sandboxing or virtualization techniques when processing untrusted PDF documents to limit the potential impact of successful exploitation attempts.