CVE-2026-21304 is a heap-based buffer overflow vulnerability (CWE-122) found in Adobe InDesign Desktop versions 21.0, 19.5.5, and earlier. The vulnerability arises from improper handling of heap memory when processing certain crafted files, which can lead to memory corruption. An attacker can exploit this flaw by convincing a user to open a malicious InDesign file, triggering the overflow and enabling arbitrary code execution within the context of the current user. The vulnerability does not require prior authentication but does require user interaction, specifically opening the malicious file. The CVSS v3.1 base score is 7.8, reflecting high impact on confidentiality, integrity, and availability, with low attack complexity and no privileges required. Although no known exploits have been reported in the wild, the potential for targeted attacks exists, especially against organizations relying heavily on Adobe InDesign for desktop publishing and creative workflows. The vulnerability could be leveraged to deploy malware, steal sensitive data, or disrupt operations. Adobe has not yet published patches, so organizations must monitor for updates and apply them promptly once available.

For European organizations, the impact of this vulnerability can be significant, especially for those in media, publishing, advertising, and design sectors where Adobe InDesign is widely used. Successful exploitation could lead to unauthorized code execution, data theft, or disruption of publishing workflows. Confidentiality is at risk as attackers could access sensitive design files or intellectual property. Integrity could be compromised by altering documents or injecting malicious content. Availability could be affected if the exploit causes application crashes or system instability. Given the high CVSS score and the widespread use of Adobe products in Europe, organizations may face operational and reputational damage. Additionally, attackers could use this vulnerability as a foothold for further lateral movement within corporate networks. The requirement for user interaction limits mass exploitation but targeted spear-phishing campaigns remain a viable threat vector.

1. Monitor Adobe security advisories closely and apply patches immediately once Adobe releases updates addressing CVE-2026-21304. 2. Until patches are available, restrict the opening of InDesign files from untrusted or unknown sources. 3. Implement application whitelisting and sandboxing to limit the execution context of Adobe InDesign. 4. Employ endpoint detection and response (EDR) solutions with heuristic and behavioral analysis to detect anomalous activities related to document processing. 5. Conduct user awareness training focusing on the risks of opening unsolicited or suspicious files, emphasizing the importance of verifying file sources. 6. Use network segmentation to isolate workstations running Adobe InDesign from critical infrastructure to limit lateral movement in case of compromise. 7. Regularly back up critical design files and ensure backups are stored securely offline to mitigate potential data loss or ransomware scenarios. 8. Review and tighten email filtering rules to reduce the likelihood of malicious file delivery via phishing campaigns.