CVE-2026-21304 is a heap-based buffer overflow vulnerability identified in Adobe InDesign Desktop versions 21.0, 19.5.5, and earlier. The vulnerability arises from improper handling of memory buffers during file processing, which can lead to overwriting heap memory. When a user opens a maliciously crafted InDesign file, the overflow can be triggered, enabling an attacker to execute arbitrary code within the context of the current user. This could allow attackers to compromise system confidentiality, integrity, and availability by running malicious payloads, installing malware, or manipulating documents. The vulnerability requires user interaction—specifically, opening a malicious file—but does not require any prior authentication or elevated privileges. The CVSS v3.1 base score is 7.8, reflecting high severity due to the combination of local attack vector, low attack complexity, no privileges required, required user interaction, and high impact on confidentiality, integrity, and availability. As of the publication date, no public exploits have been reported, but the vulnerability poses a significant risk to users of affected Adobe InDesign versions. The lack of available patches at the time of reporting necessitates proactive mitigation strategies.

The exploitation of this vulnerability can lead to arbitrary code execution, allowing attackers to gain control over affected systems with the privileges of the current user. This can result in data theft, unauthorized modification or deletion of files, installation of persistent malware, and disruption of normal operations. Organizations relying on Adobe InDesign Desktop for document creation and publishing, especially in creative industries, marketing, and media, face risks of intellectual property theft and operational downtime. Since exploitation requires user interaction, social engineering or phishing campaigns could be used to deliver malicious files. The vulnerability affects confidentiality, integrity, and availability, potentially impacting sensitive business data and workflows. The high CVSS score indicates a serious threat that could be leveraged in targeted attacks or broader campaigns once exploit code becomes available.

1. Apply official Adobe patches immediately once released to remediate the vulnerability. 2. Until patches are available, restrict the opening of InDesign files from untrusted or unknown sources. 3. Implement strict email filtering and attachment scanning to block potentially malicious files. 4. Educate users about the risks of opening unsolicited or suspicious files, emphasizing caution with InDesign documents. 5. Employ endpoint detection and response (EDR) solutions capable of monitoring for anomalous behavior related to InDesign processes. 6. Use application whitelisting to limit execution of unauthorized code. 7. Regularly back up critical data to enable recovery in case of compromise. 8. Monitor security advisories from Adobe and threat intelligence feeds for updates on exploit availability or additional mitigations.