CVE-2026-21260: Microsoft 365 Apps for Enterprise · Information Exposure
Affects Microsoft 365 Apps for EnterpriseSource CVE Database V5
Not known to be exploited · CVSS 7.5 High : upgrade to 16.0.5539.1002 soon.
Data as of 25 Oct 2026, 19:02 UTC
- EPSS
- 1.5% chance of exploitation in 30 days – higher than 74% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 16.0.5539.1002, 16.0.10417.20097, 16.0.19127.20518
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:CExploitation evidence
Disclosed: evidence found.
CVE published 10 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.
What to do
Upgrade Microsoft to 16.0.5539.1002 (2016) or 16.0.10417.20097 (SharePoint Server 2019) or 16.0.19127.20518 (SharePoint Server Subscription Edition).
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| MicrosoftMicrosoft 365 Apps for Enterprise | Affected
| Fixed in– |
| MicrosoftMicrosoft Office 2019 | Affected
| Fixed in– |
| MicrosoftMicrosoft Office LTSC 2021 | Affected
| Fixed in– |
| MicrosoftMicrosoft Office LTSC 2024 | Affected
| Fixed in– |
| MicrosoftMicrosoft Outlook 2016 | Affected
| Fixed in
|
| MicrosoftMicrosoft SharePoint Enterprise Server 2016 | Affected
| Fixed in
|
| MicrosoftMicrosoft SharePoint Server 2019 | Affected
| Fixed in
|
| MicrosoftMicrosoft SharePoint Server Subscription Edition | Affected
| Fixed in
|
AI-suggested
An official fix is available from Microsoft, and remediation is managed by the vendor for this cloud-hosted service. Users and administrators should apply the official updates as provided in the Microsoft security advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21260 to mitigate this vulnerability.
Description
Exposure of sensitive information to an unauthorized actor in Microsoft Office Outlook allows an unauthorized attacker to perform spoofing over a network.