CVE-2025-30388 is a high-severity heap-based buffer overflow vulnerability identified in Microsoft Office LTSC for Mac 2021, specifically version 16.0.1. The vulnerability is categorized under CWE-122, indicating improper handling of memory buffers leading to overflow conditions on the heap. Although the description references Windows Win32K - GRFX, the affected product is Microsoft Office LTSC for Mac 2021, suggesting the vulnerability may stem from shared code components or a misclassification in the description. The flaw allows an unauthorized attacker to execute arbitrary code locally by exploiting the buffer overflow, which can corrupt memory and potentially allow privilege escalation or code execution within the context of the user running the application. The CVSS v3.1 base score is 7.8, reflecting high severity due to the combination of local attack vector (AV:L), low attack complexity (AC:L), no privileges required (PR:N), but requiring user interaction (UI:R). The impact metrics indicate high confidentiality, integrity, and availability impacts (C:H/I:H/A:H), meaning successful exploitation could lead to full compromise of the affected system's data and operations. No known exploits are currently reported in the wild, and no patches or mitigations are linked yet, indicating this is a newly disclosed vulnerability. The vulnerability's scope is unchanged (S:U), meaning the impact is confined to the vulnerable component without affecting other system components directly. The vulnerability is critical for users running the specified version of Microsoft Office LTSC for Mac 2021, as it could allow attackers to execute arbitrary code locally, potentially leading to further system compromise if combined with other vulnerabilities or misconfigurations.

For European organizations, this vulnerability poses a significant risk, especially those relying on Microsoft Office LTSC for Mac 2021 in their operational environments. The ability for an attacker to execute arbitrary code locally can lead to data breaches, unauthorized access to sensitive information, and disruption of business processes. Given the high confidentiality, integrity, and availability impacts, exploitation could result in loss or corruption of critical documents, intellectual property theft, or ransomware deployment. Organizations in sectors such as finance, healthcare, legal, and government, where Mac usage is prevalent and data sensitivity is high, are particularly vulnerable. The requirement for user interaction means phishing or social engineering campaigns could be used to trick users into triggering the exploit, increasing the attack surface. Additionally, the lack of current patches means organizations must rely on interim mitigations, increasing exposure time. The vulnerability could also be leveraged as a foothold for lateral movement within networks if attackers gain local code execution on Mac endpoints, complicating incident response and remediation efforts.

Given the absence of an official patch at this time, European organizations should implement several specific mitigations: 1) Restrict use of Microsoft Office LTSC for Mac 2021 version 16.0.1 to trusted users and environments only, minimizing exposure. 2) Employ application whitelisting and endpoint protection solutions capable of detecting anomalous behavior or exploitation attempts related to buffer overflows. 3) Educate users on the risks of phishing and social engineering attacks that could trigger the required user interaction for exploitation, emphasizing caution with unsolicited documents or links. 4) Monitor system logs and endpoint telemetry for signs of local code execution or memory corruption events. 5) Where possible, limit user privileges on Mac systems to reduce the impact of local code execution. 6) Consider deploying network segmentation to isolate Mac endpoints running the vulnerable software from critical infrastructure. 7) Stay alert for official patches or updates from Microsoft and plan rapid deployment once available. 8) Use macOS built-in security features such as System Integrity Protection (SIP) and Gatekeeper to reduce exploitation likelihood. 9) Conduct vulnerability scanning and asset inventory to identify all affected systems to prioritize remediation efforts.