CVE entry · CVE-2026-41091
CVE-2026-41091: Microsoft Defender Link Following Vulnerability
Microsoft Defender contains a link following vulnerability that allows an authorized attacker to elevate privileges locally.
- Actively exploited: added to CISA’s KEV catalog on May 20, 2026.
- Use by ransomware: not established so far.
- Remediation deadline for US federal agencies: June 3, 2026.
Description from CISA’s KEV catalog.
What to do
- Check whether your estate includes Microsoft Defender, including internet-facing devices.
- Apply the vendor’s patch or mitigations (references below). Failing that, isolate the product or stop using it, as CISA requires of US federal agencies.
- An exploited vulnerability has often been used before it was fixed: look for signs of compromise, especially on internet-facing devices.
References
- Vendor advisory or reference cited by CISA (msrc.microsoft.com)
- NVD entry (NIST)
- CISA KEV catalog
Other Microsoft vulnerabilities
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Microsoft Windows Command Injection Vulnerability
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Microsoft SharePoint Code Injection Vulnerability
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Microsoft Windows Heap-Based Buffer Overflow Vulnerability
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Microsoft Windows Link Following Vulnerability
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Microsoft SQL Server Remote Code Execution Vulnerability
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Microsoft SharePoint Weak Authentication Vulnerability