CVE-2023-41764 is a vulnerability identified in Microsoft Office 2019 (version 19.0.0) characterized by improper verification of cryptographic signatures, classified under CWE-347. This weakness means that Microsoft Office does not correctly validate the authenticity of cryptographic signatures on certain content, allowing an attacker to spoof or forge signed documents or elements within documents. The flaw specifically impacts the integrity of the data, as an attacker can manipulate content to appear as if it is legitimately signed or trusted, potentially misleading users or automated systems relying on signature validation. The vulnerability requires local access (attack vector: local) and user interaction to exploit, with no privileges required, indicating that an attacker must trick a user into opening or interacting with a maliciously crafted document. The CVSS v3.1 base score is 5.5 (medium severity), reflecting limited attack scope and complexity but a significant impact on data integrity. No exploits have been reported in the wild as of the publication date (September 12, 2023). The absence of patches at the time of reporting suggests that organizations should monitor for updates from Microsoft and apply them promptly once available. This vulnerability could be leveraged in targeted phishing or social engineering campaigns where attackers craft documents that appear authentic due to forged signatures, increasing the likelihood of successful compromise or misinformation.

For European organizations, the primary impact of CVE-2023-41764 lies in the potential for document spoofing and integrity compromise. Attackers could use this vulnerability to create malicious documents that appear legitimately signed, undermining trust in document authenticity. This can facilitate phishing attacks, fraud, or misinformation campaigns, especially in sectors relying heavily on signed documents such as finance, legal, and government. While confidentiality and availability are not directly affected, the integrity breach can lead to significant operational and reputational damage. Organizations with workflows that depend on cryptographic signature validation for document approval or compliance may face increased risk of unauthorized actions or decisions based on forged documents. The requirement for local access and user interaction limits mass exploitation but does not eliminate risk in environments with high user exposure to external documents or email attachments. Given the widespread use of Microsoft Office 2019 across Europe, the vulnerability could be exploited in targeted attacks against high-value entities.

To mitigate CVE-2023-41764, European organizations should: 1) Monitor Microsoft’s official channels for patches and apply updates immediately once released. 2) Implement strict policies to disable or restrict macros and active content in Office documents, especially from untrusted sources. 3) Educate users to recognize suspicious documents and avoid opening attachments or links from unknown or unverified senders. 4) Employ advanced email filtering and sandboxing solutions to detect and block malicious documents before reaching end users. 5) Use endpoint protection tools capable of detecting anomalous document behavior or signature forgery attempts. 6) Enforce multi-factor authentication and least privilege principles to reduce the impact of potential social engineering attacks leveraging spoofed documents. 7) Review and strengthen document verification workflows to include additional validation steps beyond cryptographic signatures where feasible. These measures collectively reduce the risk of exploitation and limit the potential damage from forged or spoofed documents.