CVE-2025-54895 is an integer overflow or wraparound vulnerability identified in the SPNEGO Extended Negotiation component of Microsoft Windows 10 Version 1809 (build 17763.0). SPNEGO (Simple and Protected GSSAPI Negotiation Mechanism) is used for negotiating authentication protocols, and the Extended Negotiation feature handles additional negotiation data. The vulnerability stems from improper validation of integer values during negotiation processing, which can cause an integer overflow or wraparound. This flaw can be exploited by an attacker with authorized local access and low privileges to escalate their privileges to higher levels, potentially SYSTEM or administrator. The attack does not require user interaction, increasing its risk. The vulnerability impacts confidentiality, integrity, and availability, as an attacker could gain control over the system, access sensitive data, or disrupt services. The CVSS v3.1 score of 7.8 (AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H) indicates that while the attack vector is local and requires high attack complexity, the privileges required are low, and the scope is changed, affecting multiple system components. No public exploits are known yet, and no patches have been released at the time of publication, but the vulnerability is officially published and reserved by Microsoft. The CWE-190 classification confirms the root cause as an integer overflow, a common programming error leading to security issues.

For European organizations, this vulnerability poses a significant risk, particularly in sectors where Windows 10 Version 1809 remains in use, such as government agencies, healthcare, finance, and critical infrastructure. Successful exploitation could allow attackers to elevate privileges locally, bypassing security controls and gaining unauthorized access to sensitive information or administrative functions. This could lead to data breaches, disruption of services, or deployment of further malware. The lack of required user interaction and the potential for complete system compromise increase the threat level. Organizations relying on legacy systems or delayed patch cycles are especially vulnerable. The impact extends to compliance risks under GDPR if personal data confidentiality is compromised. Additionally, the vulnerability could be leveraged in targeted attacks against strategic European entities, amplifying geopolitical risks.

1. Immediate mitigation includes restricting local access to systems running Windows 10 Version 1809 by enforcing strict access controls and monitoring for unusual privilege escalation attempts. 2. Deploy host-based intrusion detection systems (HIDS) to detect anomalous behavior indicative of exploitation attempts. 3. Apply principle of least privilege to limit user rights and reduce the attack surface. 4. Prepare for patch deployment by inventorying affected systems and testing updates in controlled environments once Microsoft releases patches. 5. Consider upgrading affected systems to newer, supported Windows versions where this vulnerability is not present. 6. Implement network segmentation to isolate critical systems and reduce lateral movement opportunities. 7. Conduct user awareness training focused on recognizing signs of local compromise and reporting suspicious activity. 8. Maintain up-to-date backups to enable recovery in case of successful exploitation.