CVE-2021-21098 is an out-of-bounds write vulnerability (CWE-787) found in Adobe InDesign version 16.0 and earlier. This vulnerability arises when Adobe InDesign parses a specially crafted file, leading to memory corruption due to writing data outside the intended buffer boundaries. Such out-of-bounds writes can corrupt adjacent memory, potentially allowing an attacker to execute arbitrary code within the context of the current user. Exploitation requires that the victim opens a maliciously crafted InDesign file, meaning user interaction is necessary. The attacker does not need to be authenticated to exploit this vulnerability, as the attack vector is through file parsing. While no known exploits have been reported in the wild, the vulnerability poses a risk of remote code execution (RCE), which could allow attackers to run arbitrary commands or malware on the affected system. The lack of a publicly available patch link suggests that remediation may require updating to a newer, unaffected version of Adobe InDesign or applying vendor-supplied patches once available. Given the nature of the vulnerability, it primarily threatens the confidentiality, integrity, and availability of systems where Adobe InDesign is used, especially in environments where users frequently open files from untrusted sources.

For European organizations, the impact of CVE-2021-21098 could be significant in sectors relying heavily on Adobe InDesign for publishing, marketing, and creative content production. Successful exploitation could lead to unauthorized code execution, enabling attackers to steal sensitive data, deploy ransomware, or establish persistent footholds within corporate networks. The threat is particularly relevant to organizations with distributed creative teams or those that exchange InDesign files with external partners, increasing the risk of receiving malicious files. Compromise of user workstations could lead to lateral movement within networks, potentially affecting broader IT infrastructure. Additionally, organizations in regulated industries such as media, advertising, and publishing could face reputational damage and compliance issues if sensitive content or intellectual property is exposed or manipulated. The requirement for user interaction somewhat limits the attack surface but does not eliminate risk, especially in environments where social engineering or phishing tactics could be used to trick users into opening malicious files.

1. Ensure all Adobe InDesign installations are updated to the latest version provided by Adobe, as newer versions typically address known vulnerabilities. 2. Implement strict file handling policies that restrict opening InDesign files from untrusted or unknown sources. 3. Employ endpoint protection solutions capable of detecting and blocking malicious file behaviors or exploitation attempts targeting Adobe products. 4. Conduct user awareness training focused on the risks of opening unsolicited or suspicious files, emphasizing verification of file origins. 5. Use application whitelisting or sandboxing techniques to isolate Adobe InDesign processes, limiting the potential impact of exploitation. 6. Monitor network and endpoint logs for unusual activity that could indicate exploitation attempts, such as unexpected process launches or memory anomalies. 7. Coordinate with IT and security teams to establish rapid incident response procedures in case of suspected compromise related to Adobe InDesign files. 8. Where possible, disable or limit macros and scripting features within Adobe InDesign that could be leveraged in conjunction with this vulnerability.