CVE-2017-16401 in Acrobat Reader
Summary
by MITRE
An issue was discovered in Adobe Acrobat and Reader: 2017.012.20098 and earlier versions, 2017.011.30066 and earlier versions, 2015.006.30355 and earlier versions, and 11.0.22 and earlier versions. This vulnerability occurs as a result of a computation that reads data that is past the end of the target buffer; the computation is part of an image conversion, specifically in Enhanced Metafile Format Plus (EMF +) processing modules. The use of an invalid (out-of-range) pointer offset during access of internal data structure fields causes the vulnerability. A successful attack can lead to sensitive data exposure.
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Analysis
by VulDB Data Team • 09/03/2024
This vulnerability exists in Adobe Acrobat and Reader software versions prior to specific patches, representing a classic buffer overflow condition that manifests during image processing operations. The flaw specifically affects the Enhanced Metafile Format Plus (EMF+) processing modules within the software's image conversion pipeline, where improper bounds checking allows for out-of-bounds memory access. The vulnerability stems from a computation that calculates memory offsets without adequate validation of boundary conditions, resulting in a situation where the application attempts to read data beyond the allocated buffer limits. This type of issue falls under the CWE-125 vulnerability category, which describes out-of-bounds read conditions that can lead to information disclosure and potential system compromise. The flaw is particularly concerning because it occurs during routine document processing operations, making it exploitable through maliciously crafted PDF files that contain specially constructed EMF+ graphics data.
The technical implementation of this vulnerability involves the software's handling of image conversion processes where internal data structures are accessed using pointer arithmetic that does not properly validate memory boundaries. When processing EMF+ formatted graphics data, the application performs computations to determine memory offsets for accessing internal fields, but fails to verify that these offsets remain within valid memory ranges. This results in a pointer arithmetic error that causes the application to read memory locations that extend beyond the intended buffer boundaries, potentially exposing sensitive data from adjacent memory regions. The vulnerability's exploitation requires a malicious PDF document containing crafted EMF+ graphics that trigger the problematic code path during document rendering or processing. This attack vector aligns with the ATT&CK technique T1203, which involves exploitation of software vulnerabilities for information gathering purposes, and represents a form of information disclosure that could potentially reveal system memory contents including credentials, encryption keys, or other sensitive information.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable more sophisticated attacks depending on the system environment and memory layout. An attacker who successfully exploits this vulnerability could gain access to sensitive data stored in adjacent memory regions, potentially including other applications' memory contents, system credentials, or cryptographic material. The vulnerability affects multiple versions of Adobe Reader and Acrobat, indicating a widespread exposure across different software releases, which increases the potential attack surface. The nature of the flaw suggests that exploitation would require crafting specific malicious PDF documents that trigger the EMF+ processing path, making this a targeted attack rather than a mass vulnerability. However, the ease with which such documents could be distributed through phishing campaigns or malicious websites makes this vulnerability particularly dangerous in real-world scenarios. Organizations using affected versions of Adobe Acrobat and Reader should consider this vulnerability as a potential entry point for advanced persistent threats that could leverage the information disclosure for further exploitation, including credential theft or privilege escalation attacks. The vulnerability demonstrates the critical importance of proper memory management practices and boundary validation in security-critical applications, particularly those handling untrusted input data from external sources.
Mitigation strategies for this vulnerability should include immediate application of Adobe's security patches and updates, which address the buffer overflow condition through proper bounds checking mechanisms. System administrators should implement comprehensive patch management procedures to ensure all affected versions are updated promptly, as this vulnerability has been actively exploited in the wild. Additional protective measures include implementing Adobe Reader sandboxing features, restricting PDF file handling capabilities, and deploying network-based security controls to filter potentially malicious PDF content before it reaches end-user systems. The vulnerability highlights the importance of secure coding practices such as implementing proper input validation, using safe memory management functions, and conducting thorough security testing of image processing modules. Organizations should also consider implementing application whitelisting policies that restrict execution of untrusted PDF processing operations and monitor for unusual PDF processing activities that might indicate exploitation attempts. Regular security assessments of document processing components and memory handling routines should be conducted to identify similar vulnerabilities in other applications and systems that might be susceptible to analogous buffer overflow conditions.