CVE-2026-21260
Published: 10 February 2026
Summary
CVE-2026-21260 is a high-severity Exposure of Sensitive Information to an Unauthorized Actor (CWE-200) vulnerability in Microsoft Office Long Term Servicing Channel. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 22.3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 AU-13 (Monitoring for Information Disclosure) and RA-5 (Vulnerability Monitoring and Scanning).
Deeper analysis
CVE-2026-21260, published on 2026-02-10, is a vulnerability involving the exposure of sensitive information to an unauthorized actor in Microsoft Office Outlook. This issue, classified under CWE-200, enables an unauthorized attacker to perform spoofing over a network and carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N), indicating high confidentiality impact with network accessibility, low attack complexity, and no requirements for privileges or user interaction.
An unauthorized attacker can exploit this vulnerability remotely over the network without authentication or user involvement. Exploitation allows the attacker to access sensitive information and conduct spoofing attacks, potentially enabling further deception or reconnaissance activities.
Microsoft's Security Response Center provides guidance on mitigation and patching in its update guide at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21260.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-7354
Vulnerability details
Exposure of sensitive information to an unauthorized actor in Microsoft Office Outlook allows an unauthorized attacker to perform spoofing over a network.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Remote unauthenticated info disclosure in Outlook directly enables exploitation of a public-facing client application (T1190) and facilitates spoofing via obtained sensitive data (T1557).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly remediates the exposure of sensitive information in Microsoft Office Outlook by requiring timely application of vendor patches for CVE-2026-21260.
Identifies CVE-2026-21260 through periodic vulnerability scanning of systems running Microsoft Office Outlook, enabling proactive patching.
Monitors systems for unauthorized disclosures of sensitive information, directly addressing the information exposure exploited remotely for spoofing in this CVE.