CVE-2018-12839 in Acrobat Reader
Summary
by MITRE
Adobe Acrobat and Reader versions 2018.011.20063 and earlier, 2017.011.30102 and earlier, and 2015.006.30452 and earlier have an out-of-bounds read vulnerability. Successful exploitation could lead to information disclosure.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 08/07/2024
Adobe Acrobat and Reader contain a critical out-of-bounds read vulnerability that affects multiple version ranges including 2018.011.20063 and earlier, 2017.011.30102 and earlier, and 2015.006.30452 and earlier. This vulnerability stems from improper bounds checking within the software's handling of PDF files, specifically when processing certain embedded objects or streams. The flaw allows an attacker to craft a malicious PDF document that triggers an out-of-bounds memory read operation when the vulnerable software attempts to parse and render the file. This type of vulnerability falls under the CWE-129 category of Improper Validation of Array Index, which represents a fundamental weakness in input validation where the software fails to properly validate array indices before accessing memory locations. The security implications of this vulnerability are significant as successful exploitation can result in information disclosure, where sensitive data from adjacent memory locations may be read and potentially exfiltrated. The out-of-bounds read occurs during the parsing of PDF content, particularly when processing malformed or specially crafted elements within the document structure, which could include compressed streams, embedded fonts, or complex graphical objects. Attackers can leverage this vulnerability by delivering a malicious PDF file to unsuspecting users, who when opening the document with the vulnerable software, trigger the exploitable condition. This represents a classic client-side attack vector that aligns with ATT&CK technique T1203, which involves the exploitation of software vulnerabilities to gain access to sensitive information. The impact extends beyond simple information disclosure as the leaked memory contents could potentially include cryptographic keys, user credentials, or other sensitive data that may be stored in adjacent memory segments. The vulnerability demonstrates the critical importance of proper memory management and bounds checking in document processing software, where the parsing of untrusted input data must be rigorously validated to prevent arbitrary memory access patterns. Organizations should prioritize immediate patching of affected versions to prevent exploitation, as the vulnerability does not require user interaction beyond opening the malicious document, making it particularly dangerous in targeted attack scenarios. The flaw underscores the need for comprehensive input validation mechanisms and robust error handling in PDF rendering engines, as these components must be capable of gracefully handling malformed or malicious input without compromising system security.
The technical nature of this vulnerability highlights the complexity of PDF parsing operations and the challenges associated with validating the vast array of data structures that can be embedded within PDF documents. When Adobe Acrobat and Reader process PDF files, they must traverse complex object hierarchies, parse compressed data streams, and handle various encoding formats, each of which presents potential entry points for exploitation. The out-of-bounds read occurs specifically during the memory access patterns when the software attempts to read data beyond the allocated buffer boundaries, which can be triggered by manipulating the length fields or object references within the PDF structure. This vulnerability type is particularly concerning because it can be exploited without requiring any special privileges or user interaction beyond opening the document, making it an attractive target for threat actors seeking to conduct passive information gathering operations. The memory disclosure aspect of the vulnerability means that attackers may be able to extract sensitive information from the process memory space, potentially including session tokens, encryption keys, or other confidential data that may be temporarily stored in memory during PDF processing. Security researchers have noted that such vulnerabilities often stem from the complexity of PDF specification compliance, where the need to support extensive features and backward compatibility can introduce subtle memory handling errors that are difficult to detect during routine testing. The exploitation of this vulnerability requires careful crafting of PDF documents that can trigger the specific memory access patterns, but once successful, it provides attackers with a mechanism to extract potentially valuable information from systems running vulnerable versions of the software. Organizations should implement comprehensive patch management procedures to ensure all instances of affected Adobe Acrobat and Reader installations are updated promptly, as the vulnerability represents a persistent risk to information security across enterprise environments.
The operational impact of CVE-2018-12839 extends beyond immediate information disclosure concerns to encompass broader security implications for organizations relying on Adobe PDF processing capabilities. The vulnerability affects multiple major release versions, indicating that it may have been present for an extended period, potentially allowing threat actors to develop and refine exploitation techniques over time. This prolonged exposure period increases the likelihood that the vulnerability has been actively exploited in the wild, particularly in targeted attacks against high-value targets such as government agencies, financial institutions, or technology companies. The nature of the flaw means that organizations cannot simply rely on network-based detection measures, as the vulnerability is triggered during local processing of PDF files, making it difficult to identify through traditional network monitoring approaches. The vulnerability's classification as an out-of-bounds read also places it within the broader category of memory corruption vulnerabilities that can potentially lead to more severe exploitation outcomes if combined with other vulnerabilities or if the attacker can achieve code execution. Security teams must consider the potential for this vulnerability to be chained with other exploits to achieve more sophisticated attack objectives, such as privilege escalation or remote code execution, which would significantly increase the overall risk profile. The impact on user productivity and organizational security posture is considerable, as users may inadvertently open malicious documents while performing routine tasks such as email processing or document review, making the attack surface particularly broad. Organizations should conduct comprehensive vulnerability assessments to identify all systems running affected versions of Adobe Acrobat and Reader, and implement appropriate access controls to limit exposure while patches are deployed. The vulnerability also highlights the importance of maintaining current security awareness training programs, as users may not recognize the potential risks associated with opening PDF attachments from untrusted sources, particularly when the malicious content is designed to exploit specific software vulnerabilities rather than relying on social engineering techniques.