CVE-2021-21099 in InDesign
Summary
by MITRE • 06/28/2021
Adobe InDesign version 16.0 (and earlier) is affected by an Out-of-bounds Write vulnerability when parsing a crafted file. An unauthenticated attacker could leverage this vulnerability to achieve remote code execution in the context of the current user. Exploitation of this issue requires user interaction in that a victim must open a malicious file.
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Analysis
by VulDB Data Team • 07/03/2021
Adobe InDesign version 16.0 and earlier contains a critical out-of-bounds write vulnerability classified as CVE-2021-21099 that represents a significant security risk for users of the popular desktop publishing software. This vulnerability resides in the file parsing functionality of the application and manifests when processing specially crafted files that contain malformed data structures. The flaw allows an attacker to manipulate memory boundaries during file interpretation, potentially leading to arbitrary code execution with the privileges of the currently logged-in user. The vulnerability is particularly concerning because it requires only a single user interaction to be exploited, making it highly suitable for social engineering attacks where victims might unknowingly open malicious documents. The technical implementation of this vulnerability involves the application's failure to properly validate array bounds when processing specific file formats, creating opportunities for attackers to overwrite adjacent memory locations with malicious data. This type of vulnerability falls under the CWE-787 category of out-of-bounds write conditions, which is a well-documented weakness in software security that has been exploited in numerous high-profile attacks. The attack vector requires the victim to open a malicious file, which typically occurs through email attachments, malicious websites, or compromised documents shared through collaborative platforms. The remote code execution capability means that attackers could potentially install malware, steal sensitive data, or establish persistent access to compromised systems without requiring additional authentication or network privileges. This vulnerability aligns with ATT&CK technique T1203, which covers exploitation of remote services, and T1059, which involves command and scripting interpreters, as successful exploitation would likely involve executing malicious payloads within the InDesign application environment. The impact of this vulnerability extends beyond individual users to enterprise environments where InDesign is widely used for professional publishing workflows, potentially compromising entire document creation and design processes.
The exploitation of CVE-2021-21099 demonstrates how seemingly benign file processing operations can become attack vectors for sophisticated malware delivery mechanisms. The vulnerability's reliance on user interaction makes it particularly dangerous in targeted attack scenarios where attackers can craft convincing social engineering campaigns to encourage victims to open malicious files. Security researchers have identified that the flaw occurs during the parsing of structured document formats that InDesign uses to interpret complex layout files, where improper boundary checking allows attackers to manipulate memory allocation patterns. The memory corruption that results from this out-of-bounds write can potentially be leveraged to overwrite critical program structures, function pointers, or return addresses within the application's execution context. This vulnerability represents a classic example of how buffer overflow conditions can be exploited to achieve privilege escalation, as the executed code would run with the same privileges as the legitimate InDesign process. The affected software versions have been patched by Adobe through security updates, but organizations must ensure comprehensive deployment of these patches across all user endpoints to prevent exploitation. The vulnerability's characteristics make it particularly attractive to threat actors who may use it as part of multi-stage attack campaigns, potentially combining it with other exploitation techniques to establish more persistent and sophisticated access to target systems. Organizations should implement additional security controls such as email filtering, web application firewalls, and user education programs to reduce the likelihood of successful exploitation attempts.
Organizations utilizing Adobe InDesign should prioritize immediate patch deployment to address CVE-2021-21099 and related vulnerabilities within their security infrastructure. The vulnerability's potential for remote code execution makes it a critical priority for security teams to address through coordinated patch management processes. Users should be educated about the risks of opening untrusted documents and the importance of maintaining current software versions to protect against known exploits. Security monitoring should include detection of suspicious file opening activities and unusual network connections that might indicate exploitation attempts. The vulnerability's exploitation requires user interaction, which provides an opportunity for defensive measures such as email sandboxing and document preview restrictions to reduce attack surface. Regular security assessments should verify that all InDesign installations are updated to the latest versions and that appropriate security configurations are implemented to prevent unauthorized access. The remediation process should also include validation of the patch deployment across all user environments and verification that the vulnerability has been effectively addressed through automated testing and vulnerability scanning tools. Security teams should maintain awareness of additional vulnerabilities in the Adobe ecosystem and implement comprehensive security policies that address multiple attack vectors simultaneously. The incident response plan should include specific procedures for handling potential exploitation attempts related to this vulnerability, including forensic analysis capabilities and communication protocols for reporting security incidents.