CVE-2021-39818 in InCopy
Summary
by MITRE • 09/28/2021
Adobe InCopy version 11.1 (and earlier) is affected by a memory corruption vulnerability due to insecure handling of a malicious TIFF file, potentially resulting in arbitrary code execution in the context of the current user. User interaction is required to exploit this vulnerability.
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Analysis
by VulDB Data Team • 10/03/2021
Adobe InCopy version 11.1 and earlier versions contain a critical memory corruption vulnerability identified as CVE-2021-39818 that stems from insecure handling of maliciously crafted TIFF image files. This vulnerability falls under the Common Weakness Enumeration category CWE-121, which encompasses heap-based buffer overflow conditions where insufficient bounds checking allows attackers to write beyond allocated memory regions. The flaw specifically manifests when the application processes TIFF files that contain malformed or maliciously constructed data structures, leading to unpredictable memory corruption patterns that can be exploited to execute arbitrary code.
The technical implementation of this vulnerability involves the improper validation and processing of TIFF file metadata and image data structures within InCopy's image handling subsystem. When a user opens or previews a specially crafted TIFF file, the application's parser fails to properly validate the file format boundaries and data offsets, allowing an attacker to manipulate memory layout through carefully constructed malicious data sequences. This insecure memory handling creates opportunities for stack or heap corruption that can be leveraged to overwrite critical program execution pointers or function return addresses, ultimately enabling remote code execution within the context of the currently logged-in user account.
The operational impact of this vulnerability extends beyond simple code execution as it represents a significant elevation of privileges attack vector that can be exploited through social engineering or targeted phishing campaigns. The requirement for user interaction makes this vulnerability particularly dangerous in enterprise environments where users may inadvertently open malicious attachments or download compromised files from untrusted sources. Attackers can craft TIFF files that appear legitimate but contain hidden malicious payloads, leveraging the application's image processing capabilities to deliver their exploits. This vulnerability aligns with ATT&CK technique T1203, which covers exploitation of software vulnerabilities for privilege escalation, and T1059, which covers command and control through application execution.
Organizations should prioritize immediate remediation by updating to Adobe InCopy version 11.2 or later, which contains patches addressing the memory corruption issues in TIFF file handling. Additionally, implementing strict file validation policies and restricting user access to potentially malicious file types can significantly reduce the attack surface. Security teams should monitor network traffic for suspicious TIFF file transfers and consider deploying application whitelisting solutions that prevent unauthorized execution of vulnerable applications. The vulnerability demonstrates the critical importance of proper input validation and memory safety practices in multimedia processing applications, particularly those handling complex file formats with extensive metadata structures that require extensive parsing and interpretation.