CVE-2018-4888 in Acrobat Reader
Summary
by MITRE
An issue was discovered in Adobe Acrobat Reader 2018.009.20050 and earlier versions, 2017.011.30070 and earlier versions, 2015.006.30394 and earlier versions. This vulnerability is an instance of a use after free vulnerability. The vulnerability is triggered by a crafted PDF file that can cause a memory access violation exception in the XFA engine because of a dangling reference left as a consequence of freeing an object in the computation that manipulates internal nodes in a graph representation of a document object model used in XFA. Successful exploitation could lead to arbitrary code execution.
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Analysis
by VulDB Data Team • 07/23/2024
The vulnerability identified as CVE-2018-4888 represents a critical use after free flaw in Adobe Acrobat Reader affecting multiple version ranges including 2018.009.20050 and earlier, 2017.011.30070 and earlier, and 2015.006.30394 and earlier. This security defect resides within the XFA (XML Forms Architecture) engine which processes form data within PDF documents. The vulnerability stems from improper memory management where an object is freed from memory but references to that object remain accessible within the application's memory space, creating a dangling pointer condition. This type of vulnerability falls under CWE-416 which specifically addresses use after free conditions where memory is accessed after it has been freed, making it a prime target for exploitation by malicious actors seeking to execute arbitrary code.
The technical exploitation of this vulnerability occurs when a maliciously crafted PDF file is opened within the affected Adobe Acrobat Reader applications. The XFA engine processes the document object model representation which includes internal graph structures used for form processing and data manipulation. When the computation process handles internal nodes within this graph representation, the memory management system frees certain objects while leaving dangling references that persist in memory. This creates a scenario where subsequent memory access operations can trigger memory access violations or more dangerously, allow attackers to manipulate the freed memory regions. The vulnerability specifically manifests during the manipulation of document object model elements within the XFA processing context, making it particularly dangerous when users open untrusted PDF documents containing crafted XFA content.
The operational impact of CVE-2018-4888 extends beyond simple application crashes or memory access violations to represent a full arbitrary code execution vulnerability. Successful exploitation allows attackers to execute malicious code with the privileges of the victim user, potentially leading to complete system compromise. This makes the vulnerability particularly attractive to threat actors who can leverage it for initial access or privilege escalation within targeted environments. The attack vector is particularly concerning because PDF files are commonly used in business environments, making this vulnerability effective for phishing campaigns, supply chain attacks, or targeted operations against organizations. The vulnerability affects multiple versions of Adobe Acrobat Reader, indicating a widespread impact across various deployment scenarios including enterprise environments where these applications are commonly used for document processing and form management.
Organizations should immediately apply patches provided by Adobe to address this vulnerability, as the use after free condition creates a significant risk for exploitation. The recommended mitigation strategy involves updating to Adobe Acrobat Reader versions that contain fixes for the XFA engine memory management issues. Security teams should also implement network-based protections such as PDF content filtering and sandboxing mechanisms to reduce the risk of exploitation. Additionally, user education regarding the dangers of opening untrusted PDF files remains critical, particularly in environments where users may encounter malicious documents through email attachments or web downloads. The vulnerability aligns with ATT&CK technique T1203 which involves exploitation of software vulnerabilities for privilege escalation, and T1068 which covers the use of local privilege escalation techniques through application vulnerabilities, making it a significant concern for enterprise security operations.