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. The vulnerability arises when the software improperly handles memory boundaries while processing certain file inputs, leading to the reading of memory locations outside the intended buffer. This can result in exposure of sensitive information stored in memory, such as user data or application internals. The attack requires an attacker to craft a malicious InDesign file that, when opened by a victim, triggers the vulnerability. Since the vulnerability is a read-only flaw, it does not allow modification of memory or code execution, limiting the attacker's capabilities to information disclosure. The CVSS 3.1 base score is 5.5, reflecting a local attack vector (AV:L), low attack complexity (AC:L), no privileges required (PR:N), but requiring user interaction (UI:R). The impact is high on confidentiality (C:H), but no impact on integrity (I:N) or availability (A:N). No patches or exploits are currently publicly available, but the vulnerability is officially published and reserved by Adobe. This vulnerability is particularly relevant for organizations relying on Adobe InDesign for desktop publishing and graphic design, as sensitive project data or intellectual property could be exposed through exploitation.

For European organizations, especially those in media, publishing, advertising, and design sectors that heavily use Adobe InDesign Desktop, this vulnerability poses a risk of sensitive information leakage. Intellectual property, client data, or confidential project details stored in memory could be exposed if a user opens a maliciously crafted file. While the vulnerability does not allow code execution or system compromise, the confidentiality breach could lead to competitive disadvantages, reputational damage, or compliance issues under GDPR if personal data is involved. The requirement for user interaction reduces the likelihood of widespread automated exploitation but increases risk from targeted phishing or social engineering attacks. Organizations with remote or hybrid workforces may face elevated risk if users handle files from untrusted sources. The absence of known exploits in the wild currently limits immediate impact, but the vulnerability remains a potential vector for espionage or data theft campaigns.

1. Monitor Adobe security advisories closely and apply patches or updates as soon as Adobe releases them for affected InDesign Desktop versions. 2. Implement strict email and file handling policies to block or quarantine suspicious or unsolicited InDesign files, especially from unknown sources. 3. Educate users about the risks of opening files from untrusted or unexpected senders and encourage verification before opening. 4. Use endpoint protection solutions capable of detecting anomalous file behaviors or memory access patterns related to InDesign. 5. Employ network segmentation and least privilege principles to limit the exposure of systems running InDesign Desktop. 6. Consider sandboxing or opening untrusted files in isolated environments to prevent potential data leakage. 7. Regularly audit and monitor logs for unusual file access or application crashes that could indicate exploitation attempts.