CVE-2026-21304 is a heap-based buffer overflow vulnerability (CWE-122) affecting Adobe InDesign Desktop versions 21.0, 19.5.5, and earlier. This vulnerability arises from improper handling of heap memory during the processing of certain file inputs, allowing an attacker to overwrite memory buffers beyond their allocated size. Successful exploitation requires a victim to open a specially crafted malicious InDesign file, triggering the overflow. This can lead to arbitrary code execution within the context of the current user, potentially compromising confidentiality, integrity, and availability of the affected system. The CVSS 3.1 base score is 7.8, reflecting a high severity with attack vector local (AV:L), low attack complexity (AC:L), no privileges required (PR:N), user interaction required (UI:R), unchanged scope (S:U), and high impact on confidentiality, integrity, and availability (C:H/I:H/A:H). Although no known exploits are reported in the wild, the vulnerability poses a significant risk due to the widespread use of Adobe InDesign in creative and publishing sectors. The absence of patches at the time of publication necessitates immediate attention to mitigation strategies to prevent exploitation.

For European organizations, the impact of this vulnerability can be substantial, especially for those in industries relying heavily on Adobe InDesign, such as media, publishing, advertising, and graphic design. Exploitation could lead to unauthorized code execution, enabling attackers to steal sensitive data, manipulate documents, or disrupt business operations. Since the code execution occurs with the current user's privileges, the extent of damage depends on the user's access rights; administrative users could face full system compromise. The requirement for user interaction limits remote exploitation but does not eliminate risk, as phishing or social engineering can be used to deliver malicious files. The disruption could affect confidentiality of intellectual property and client data, integrity of published materials, and availability of critical design workstations. Given the interconnected nature of European business environments, a successful attack could propagate through networks, amplifying impact.

1. Apply official Adobe patches immediately once they become available to remediate the vulnerability. 2. Until patches are released, restrict the opening of InDesign files from untrusted or unknown sources, implementing strict email filtering and endpoint controls. 3. Educate users about the risks of opening unsolicited or suspicious files, emphasizing the importance of verifying file origins. 4. Employ endpoint detection and response (EDR) solutions with behavior-based detection to identify and block exploitation attempts. 5. Implement application whitelisting to limit execution of unauthorized code. 6. Use sandboxing or isolated environments for opening potentially risky files to contain any malicious activity. 7. Regularly back up critical design files and systems to enable recovery in case of compromise. 8. Monitor network and system logs for unusual activity indicative of exploitation attempts. 9. Coordinate with IT and security teams to enforce least privilege principles, minimizing user rights on design workstations.