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CVE-2025-52691

Critical CVSS 10 Known exploited

Published 2025-12-29 · last changed 2026-06-17 · added to CISA KEV 2026-01-26

This one is being exploited in the wild.

CISA added CVE-2025-52691 to the Known Exploited Vulnerabilities catalog on 2026-01-26. Federal agencies are required to remediate it on a deadline. If you have affected machines, this is the class of finding that moves ahead of the rest of the queue.

The fix

We hold no Microsoft remediation data for CVE-2025-52691, which normally means it is not a Windows CVE. For non-Microsoft software the fix is the vendor's own updated release, and the affected versions are listed below.

What it is

Successful exploitation of the vulnerability could allow an unauthenticated attacker to upload arbitrary files to any location on the mail server, potentially enabling remote code execution.

Sources

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H