CVE-2021-39819 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 XML 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 that stems from insecure handling of maliciously crafted XML files. This vulnerability falls under the CWE-121 category of buffer overflow conditions and represents a classic example of improper input validation that can lead to arbitrary code execution. The flaw occurs when the application processes XML content without adequate sanitization or bounds checking, allowing an attacker to craft specially malformed XML data that triggers memory corruption during parsing operations.
The technical exploitation of this vulnerability requires user interaction, meaning an attacker must convince a target to open a malicious XML file within the InCopy application. This interaction typically occurs through social engineering tactics such as phishing emails containing infected attachments or malicious links. When the vulnerable application attempts to parse the crafted XML, the insecure memory handling causes buffer overflows or memory corruption that can be leveraged to execute arbitrary code with the privileges of the currently logged-in user. The vulnerability demonstrates characteristics consistent with the ATT&CK technique T1203, where adversaries abuse application vulnerabilities to execute code, and T1059, which involves the use of command and scripting interpreter.
The operational impact of this vulnerability extends beyond simple code execution as it provides attackers with a potential foothold for further compromise within the target environment. Since InCopy is commonly used in creative workflows and document preparation processes, the attack surface is broad and includes users in design, publishing, and content creation roles who may be less security-aware. The memory corruption can result in application crashes, data loss, or complete system compromise depending on the execution context and the attacker's objectives. Organizations using older versions of Adobe InCopy face heightened risk due to the lack of modern security mitigations such as address space layout randomization and stack canaries that are typically present in more recent software versions.
Mitigation strategies should prioritize immediate patching of Adobe InCopy to version 11.2 or later, which includes fixes for this memory corruption vulnerability. Organizations should also implement strict file validation policies that prevent users from opening untrusted XML files, particularly those received through email or downloaded from untrusted sources. Network-level controls such as email filtering and web proxies can help block malicious attachments before they reach end users. Additionally, security awareness training should emphasize the dangers of opening unexpected files, and privileged users should be especially cautious when handling document files. The vulnerability demonstrates the importance of maintaining up-to-date software and following the principle of least privilege, as exploitation of such vulnerabilities often requires minimal user interaction but can result in significant security breaches. Regular security assessments of creative software environments are recommended to identify other potential attack vectors that may exist in document processing applications.