CVE-2026-21357 is a heap-based buffer overflow vulnerability (CWE-122) identified in Adobe InDesign Desktop versions 21.1, 20.5.1, and earlier. This vulnerability arises from improper handling of heap memory during file processing, which can lead to memory corruption. An attacker can exploit this flaw by convincing a user to open a maliciously crafted 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 severity due to its impact on confidentiality, integrity, and availability, combined with low attack complexity and no privileges required. Although no exploits are currently known in the wild, the potential for targeted attacks exists, especially against organizations relying heavily on Adobe InDesign for desktop publishing and creative workflows. The lack of available patches at the time of reporting necessitates immediate risk mitigation through alternative controls. This vulnerability could be leveraged to deploy malware, steal sensitive information, or disrupt operations by corrupting system processes or files.

For European organizations, the impact of CVE-2026-21357 can be significant, particularly for those in media, publishing, advertising, and design sectors that extensively use Adobe InDesign Desktop. Successful exploitation could lead to unauthorized code execution, resulting in data breaches, intellectual property theft, or ransomware deployment. The vulnerability compromises confidentiality by potentially exposing sensitive design files and client data, integrity by allowing modification of documents or system files, and availability by causing application or system crashes. Given the user interaction requirement, phishing or social engineering campaigns could be used to deliver malicious files. The disruption could affect business continuity and damage reputation. Organizations with lax endpoint security or insufficient user training are at higher risk. The absence of known exploits currently provides a window for proactive defense, but the high CVSS score indicates that once exploits emerge, the threat will escalate rapidly.

1. Monitor Adobe’s official channels for patches and apply them immediately upon release to remediate the vulnerability. 2. Until patches are available, restrict the opening of InDesign files from untrusted or unknown sources through email filtering and endpoint policies. 3. Implement robust user awareness training focused on recognizing phishing attempts and suspicious file attachments. 4. Employ application whitelisting and sandboxing to limit the execution of unauthorized code. 5. Use endpoint detection and response (EDR) solutions with behavior-based detection to identify anomalous activities indicative of exploitation attempts. 6. Enforce the principle of least privilege for user accounts running Adobe InDesign to minimize the impact of potential code execution. 7. Regularly back up critical design files and systems to enable recovery in case of compromise. 8. Consider network segmentation to isolate systems running Adobe InDesign from sensitive infrastructure. 9. Conduct regular vulnerability assessments and penetration testing to identify and address related security gaps.