CVE-2026-21277 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 when InDesign improperly handles memory allocation during the processing of certain file inputs, leading to a buffer overflow on the heap. This overflow can be exploited by an attacker to overwrite memory and execute arbitrary code within the context of the current user. The attack vector requires the victim to open a maliciously crafted InDesign file, meaning user interaction is necessary for exploitation. No prior authentication is required, increasing the attack surface. The vulnerability affects confidentiality, integrity, and availability, as arbitrary code execution can lead to data theft, system compromise, or denial of service. The CVSS v3.1 base score is 7.8, reflecting high severity with low attack complexity but requiring user interaction. Currently, no public exploits or active exploitation in the wild have been reported. Adobe has not yet published patches but is expected to do so given the vulnerability's severity. The flaw is particularly concerning for organizations relying on Adobe InDesign for desktop publishing and creative workflows, as it could be leveraged in targeted attacks or phishing campaigns distributing malicious files.

For European organizations, this vulnerability poses a significant risk, especially for those in media, publishing, advertising, and design sectors that heavily utilize Adobe InDesign Desktop. Successful exploitation could lead to unauthorized code execution, resulting in data breaches, intellectual property theft, or disruption of critical creative workflows. Since the attack requires opening a malicious file, phishing or social engineering campaigns could be used to deliver the payload, increasing the likelihood of compromise. The impact extends to confidentiality (exposure of sensitive design files), integrity (tampering with documents or system settings), and availability (potential system crashes or denial of service). Organizations with lax endpoint security or insufficient user training are particularly vulnerable. The absence of known exploits in the wild reduces immediate risk but does not eliminate the threat, as attackers may develop exploits once patches are released or if the vulnerability details become widely known.

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 through email filtering and endpoint controls. 3. Implement application whitelisting and sandboxing to limit the execution environment of Adobe InDesign, reducing the impact of potential exploitation. 4. Educate users on the risks of opening unsolicited or suspicious files, emphasizing cautious handling of email attachments and downloads. 5. Employ endpoint detection and response (EDR) tools to monitor for anomalous behavior indicative of exploitation attempts. 6. Regularly back up critical design files and systems to enable recovery in case of compromise. 7. Consider network segmentation to isolate creative workstations from sensitive or critical infrastructure. 8. Monitor threat intelligence feeds for updates on exploit development or active attacks targeting this vulnerability.