CVE-2026-21278 is an out-of-bounds read vulnerability classified under CWE-125, affecting Adobe InDesign Desktop versions 21.0, 19.5.5, and earlier. This vulnerability arises when the software improperly handles memory boundaries while processing certain file inputs, allowing an attacker to read memory locations beyond the intended buffer. The consequence is potential exposure of sensitive information stored in memory, which could include user data or application secrets. Exploitation requires the victim to open a specially crafted malicious file, meaning user interaction is mandatory. The attack vector is local (AV:L), with low attack complexity (AC:L), no privileges required (PR:N), and user interaction required (UI:R). The vulnerability does not affect integrity or availability, as it does not allow code execution or system crashes. Adobe has not yet released patches, and no known exploits are reported in the wild. The vulnerability's medium severity (CVSS 5.5) reflects the balance between the potential impact on confidentiality and the exploitation constraints. This flaw is particularly relevant for organizations relying on Adobe InDesign for desktop publishing, as sensitive project data could be exposed if malicious files are opened.

For European organizations, the primary impact is the potential leakage of sensitive information from memory when a malicious file is opened in Adobe InDesign Desktop. This could include confidential project data, client information, or intellectual property, particularly critical in creative, publishing, and media sectors. Although the vulnerability does not allow remote exploitation or code execution, the requirement for user interaction means targeted phishing or social engineering attacks could be used to deliver malicious files. The impact on confidentiality could lead to reputational damage, regulatory compliance issues (e.g., GDPR), and financial loss if sensitive data is exposed. Since the vulnerability does not affect system integrity or availability, operational disruption is unlikely. However, organizations with high volumes of file exchange or collaboration using InDesign are at greater risk. The absence of known exploits reduces immediate threat but does not eliminate future risk, especially as attackers develop new techniques.

1. Monitor Adobe security advisories closely and apply patches immediately once available to affected InDesign Desktop versions. 2. Implement strict file handling policies, including scanning all incoming files with advanced malware detection tools before opening in InDesign. 3. Educate users on the risks of opening files from untrusted sources and enforce the use of sandboxed or isolated environments for opening unknown files. 4. Employ endpoint detection and response (EDR) solutions to monitor for suspicious activity related to file handling and memory access. 5. Restrict the use of older InDesign versions by upgrading to the latest supported releases that may include security improvements. 6. Use network segmentation to limit exposure of critical systems running InDesign, reducing the risk of lateral movement if exploitation occurs. 7. Maintain regular backups and incident response plans to quickly address any potential data exposure incidents. 8. Consider disabling automatic file previews or thumbnails in file explorers to reduce accidental triggering of malicious files.