CVE-2021-21060 is an improper input validation vulnerability (CWE-20) affecting multiple versions of Adobe Acrobat Reader, specifically Adobe Acrobat Pro DC versions 2020.013.20074 and earlier, 2020.001.30018 and earlier, and 2017.011.30188 and earlier. The vulnerability arises because the software does not adequately validate input data when processing PDF files. An unauthenticated attacker can exploit this flaw by crafting a malicious PDF file that, when opened by a victim using a vulnerable version of Acrobat Reader, can lead to the disclosure of sensitive information within the context of the current user. This means that the attacker can potentially access data that the user has permission to view but should not be exposed through the application. Exploitation requires user interaction, specifically the victim opening the malicious PDF file, which is a common attack vector for document-based vulnerabilities. There are no known exploits in the wild reported for this vulnerability, and no official patches or updates are linked in the provided information, though Adobe typically addresses such issues in security updates. The vulnerability impacts confidentiality primarily, as it allows information disclosure, but does not directly affect system integrity or availability. Since the attacker does not need to be authenticated but does require the user to open a malicious file, the attack vector is user-dependent and somewhat limited in scope. The vulnerability affects widely used versions of Adobe Acrobat Reader, a prevalent PDF reader in both enterprise and consumer environments worldwide.

For European organizations, the impact of CVE-2021-21060 can be significant due to the widespread use of Adobe Acrobat Reader in business, government, and educational institutions. The vulnerability could lead to unauthorized disclosure of sensitive information such as confidential documents, personal data, or intellectual property if a user opens a malicious PDF. This could result in data breaches, regulatory non-compliance (e.g., GDPR violations), reputational damage, and potential financial losses. Since the vulnerability requires user interaction, targeted phishing campaigns or social engineering attacks could be used to deliver malicious PDFs, increasing the risk to organizations with less mature security awareness programs. The impact is more pronounced in sectors handling sensitive or regulated data, such as finance, healthcare, legal, and public administration. However, the lack of known active exploitation and the medium severity rating suggest that while the risk is real, it is not currently widespread or critical. Organizations that do not promptly update or mitigate this vulnerability remain exposed to potential future exploitation.

1. Apply official Adobe security updates as soon as they become available. Even though no patch links are provided, organizations should verify with Adobe's security advisories and update Acrobat Reader to the latest version. 2. Implement strict email filtering and attachment scanning to detect and block malicious PDFs before they reach end users. 3. Enhance user security awareness training focusing on the risks of opening unsolicited or suspicious PDF attachments, emphasizing the importance of verifying the source. 4. Employ application whitelisting or sandboxing technologies to restrict the execution environment of Acrobat Reader, limiting the potential impact of malicious files. 5. Use endpoint detection and response (EDR) solutions to monitor for unusual behaviors related to PDF processing or information disclosure attempts. 6. Consider disabling JavaScript execution within Acrobat Reader if not required, as this can reduce the attack surface for PDF-based exploits. 7. Regularly audit and monitor sensitive data access logs to detect any anomalous access patterns that could indicate exploitation attempts.