A new security flaw has been found in Microsoft Defender. It affects Microsoft Defender for Endpoint specifically. Attackers with local access can elevate their privileges. They could gain SYSTEM level access, giving full control. This vulnerability is tracked as CVE-2025-26684. Microsoft patched it in its May 2025 security updates. These updates were released on May 13, 2025. Researchers found an “external control of filename or path” weakness. The flaw has a CVSS score of 6.7, rated “Important.”
Successful exploitation of this flaw grants SYSTEM privileges. This provides attackers with complete control over a system. Malicious actors could then install various programs. They could also modify or delete existing data. Creating new accounts with full admin rights is possible. The vulnerability comes from improper validation of user input. This specifically relates to how file paths are handled. Attackers can manipulate file operations to access restricted resources.
Cybersecurity expert Rich Mirch helped discover this particular flaw.
This vulnerability affects Microsoft Defender for Endpoint for Linux. Specifically, versions prior to 101.25XXX are vulnerable. Organizations must apply the latest security update immediately. Microsoft assessed its exploitability as “Exploitation Unlikely.” This suggests a low chance of widespread attacks. The company confirmed no prior public disclosure. There was no evidence of exploitation before the patch. The flaw was found through coordinated vulnerability disclosure. Researchers astraleureka and Rich Mirch received credit.
This vulnerability was one of 78 flaws addressed.
These were part of May 2025’s Patch Tuesday. Administrators can verify the update installation. They can use the MDE Client Analyzer tool. If unpatched, the analyzer shows a warning. Promptly applying security patches is crucial. This is especially true for security products themselves. Vulnerabilities in such tools pose significant risks. Organizations should prioritize these updates. If patching is delayed, monitor for suspicious activity. Look for privilege escalation attempts.
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