CVE-2017-16395 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. The vulnerability is caused by a buffer access with an incorrect length value in the image conversion module when processing Enhanced Metafile Format (EMF). Crafted EMF input (EMR_STRETCHDIBITS) causes a mismatch between allocated buffer size and the access allowed by the computation. If an attacker can adequately control the accessible memory then this vulnerability can be leveraged to achieve arbitrary code execution.
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Analysis
by VulDB Data Team • 01/24/2021
The vulnerability identified as CVE-2017-16395 represents a critical buffer overflow condition within Adobe Acrobat and Reader applications that affects multiple version ranges including 2017.012.20098 and earlier, 2017.011.30066 and earlier, 2015.006.30355 and earlier, and 11.0.22 and earlier versions. This flaw exists within the image conversion module specifically when processing Enhanced Metafile Format (EMF) files, particularly those containing the EMR_STRETCHDIBITS record type. The root cause stems from an incorrect length calculation that creates a mismatch between the buffer size allocated for memory operations and the actual access dimensions computed during EMF processing. This fundamental miscalculation creates a scenario where the application attempts to write data beyond the bounds of the allocated memory buffer, establishing a potential pathway for malicious code execution.
The technical exploitation of this vulnerability occurs through careful crafting of EMF input files that leverage the EMR_STRETCHDIBITS command to trigger the buffer overflow condition. When Adobe Acrobat or Reader processes these maliciously constructed files, the image conversion module fails to properly validate the length parameters associated with the EMR_STRETCHDIBITS operation, resulting in an incorrect buffer size allocation. The computation error manifests when the application calculates the memory requirements for processing the image data, leading to a situation where the actual memory access exceeds the allocated buffer boundaries. This buffer overflow condition creates opportunities for attackers to overwrite adjacent memory locations and potentially inject or redirect execution flow to malicious code.
From an operational security perspective, this vulnerability presents significant risks to organizations relying on Adobe Acrobat and Reader for document processing and viewing. The ability to achieve arbitrary code execution through crafted EMF files means that attackers can potentially gain complete control over affected systems without requiring user interaction beyond opening a malicious document. The vulnerability's impact extends beyond simple document viewing as it affects the core image processing capabilities of these applications, making it particularly dangerous in enterprise environments where PDF and EMF documents are frequently exchanged. Security practitioners must consider that this vulnerability can be exploited through various attack vectors including email attachments, web downloads, and document sharing platforms, making it a high-priority target for exploitation.
The vulnerability aligns with CWE-122, which describes "Heap-based Buffer Overflow" conditions where insufficient validation of buffer sizes leads to memory corruption. This classification reflects the fundamental nature of the flaw where the application's memory management fails to properly enforce buffer boundaries during EMF processing operations. The attack pattern follows typical exploit methodologies described in the MITRE ATT&CK framework under techniques such as T1059.007 for command and scripting interpreter and T1203 for Exploitation for Client Execution, where adversaries leverage application vulnerabilities to execute arbitrary code on target systems. Organizations should implement immediate mitigation strategies including applying the latest security patches from Adobe, implementing network-based restrictions on EMF file processing, and deploying application whitelisting controls to prevent execution of vulnerable versions of Acrobat and Reader.
Mitigation efforts must prioritize the immediate application of Adobe's security patches that address the buffer overflow condition in the image conversion module. System administrators should also consider implementing restrictive file handling policies that limit processing of EMF files through Acrobat and Reader applications, particularly when these files originate from untrusted sources. Network security controls such as deep packet inspection and file type filtering can help prevent malicious EMF files from reaching end-user systems. Additionally, organizations should conduct comprehensive vulnerability assessments to identify all systems running affected versions of Adobe Acrobat and Reader, and establish monitoring procedures to detect potential exploitation attempts. The remediation process should include not only patch deployment but also user education regarding the dangers of opening untrusted document files and the importance of maintaining current software versions to protect against known vulnerabilities.