Microsoft 365 Apps for Enterprise: Access of Resource Using Incompatible Type
CVE-2026-65807 is a high-severity access of resource using incompatible type vulnerability in Microsoft 365 Apps for Enterprise from Microsoft, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists version https://aka.ms/OfficeSecurityReleases as the first without the flaw, so updating Microsoft 365 Apps for Enterprise to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.82% chance of exploitation within 30 days, higher than 58% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Microsoft 365 Apps for Enterprise to https://aka.ms/OfficeSecurityReleases or a later version.
- Update Microsoft Excel 2016 to 16.0.5565.1001 or a later version.
- Update Microsoft Office 2019 to https://aka.ms/OfficeSecurityReleases or a later version.
- Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Microsoft | Microsoft 365 Apps for Enterprise | 16.0.1 up to, but not including, https://aka.ms/OfficeSecurityReleases | https://aka.ms/OfficeSecurityReleases |
| Microsoft | Microsoft Excel 2016 | 16.0.0.0 up to, but not including, 16.0.5565.1001 | 16.0.5565.1001 |
| Microsoft | Microsoft Office 2019 | 19.0.0 up to, but not including, https://aka.ms/OfficeSecurityReleases | https://aka.ms/OfficeSecurityReleases |
| Microsoft | Microsoft Office 365 for Mac | 1.0.0 up to, but not including, 16.112.26081010 | 16.112.26081010 |
| Microsoft | Microsoft Office LTSC 2021 | 16.0.1 up to, but not including, https://aka.ms/OfficeSecurityReleases | https://aka.ms/OfficeSecurityReleases |
| Microsoft | Microsoft Office LTSC 2024 | 16.0.0 up to, but not including, https://aka.ms/OfficeSecurityReleases | https://aka.ms/OfficeSecurityReleases |
| Microsoft | Microsoft Office LTSC for Mac 2021 | 16.0.1 up to, but not including, 16.112.26081010 | 16.112.26081010 |
| Microsoft | Microsoft Office LTSC for Mac 2024 | 16.0.0 up to, but not including, 16.112.26081010 | 16.112.26081010 |
| Microsoft | Office Online Server | 16.0.0.0 up to, but not including, 16.0.10417.20175 | 16.0.10417.20175 |
| Microsoft | 365 Apps | Not specified in the record | Not stated |
| Microsoft | Excel | 2016 | Not stated |
| Microsoft | Microsoft 365 | Not specified in the record | Not stated |
| Microsoft | Office 2019 | Not specified in the record | Not stated |
| Microsoft | Office 2021 | Not specified in the record | Not stated |
| Microsoft | Office 2024 | Not specified in the record | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. Scored by CNA (microsoft.com).
Official description
Access of resource using incompatible type ('type confusion') in Microsoft Office Excel allows an unauthorized attacker to execute code over a network.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Access of Resource Using Incompatible Type
The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.
More Access of Resource Using Incompatible Type vulnerabilities (CWE-843)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other vulnerabilities in Microsoft 365 Apps for Enterprise
- 8.8 High severity
- 6.5 Medium severity
Recent Access of Resource Using Incompatible Type vulnerabilities
- 7.5 High severity
- 7.2 High severity
- 9.8 Critical severity
- 8.8 High severity
- 9.6 Critical severity
- 8.8 High severity
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