Microsoft Security Update Guide · Office / Microsoft 365 Apps
Microsoft Office Word Information Disclosure Vulnerability
Published
What does this mean?
- Information Disclosure. An attacker can see information that is not meant for them.
- It can be exploited with access to the device itself, with an ordinary user account and without any user action.
- CVSS 5.5 out of 10: medium. Microsoft rates it Important.
- No attacks reported; Microsoft expects exploitation to be less likely.
- What should you do? Install the security update for the version you run (or a later cumulative update):
- Windows Server 2012 R2 (Server Core installation): KB5123066
6.3.9600.23398 - Windows Server 2012 R2: KB5123066
6.3.9600.23398 - Windows Server 2012 (Server Core installation): KB5123065
6.2.9200.26349 - Windows Server 2012: KB5123065
6.2.9200.26349 - Windows Server 2016 (Server Core installation): KB5123099
10.0.14393.9512 - Windows Server 2016: KB5123099
10.0.14393.9512
- Windows Server 2012 R2 (Server Core installation): KB5123066
Use after free in Microsoft Office Word allows an authorized attacker to disclose information locally.
What kind of flaw is this?
- CWE-416: Use After Free
The program uses memory after it was freed (use after free), which can lead to running code.
Key facts
Released
8 sep 2026
Impact
Information Disclosure
Max severity
Important
Weakness
CVSS 3.1
5.5 / 4.8 (base / temporal)
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:CPublicly disclosed
No
Exploited
No
Exploitability assessment
Exploitation Less Likely
Customer action required
Yes
Links
CVSS metrics
| Base score metrics | |
|---|---|
| Attack Vector | Local |
| Attack Complexity | Low |
| Privileges Required | Low |
| User Interaction | None |
| Scope | Unchanged |
| Confidentiality | High |
| Integrity | None |
| Availability | None |
| Temporal score metrics | |
| Exploit Code Maturity | Unproven |
| Remediation Level | Official Fix |
| Report Confidence | Confirmed |
Affected products and updates
| Product | Update | Build |
|---|---|---|
| Windows Server 2012 R2 (Server Core installation) | KB5123066 · Monthly Rollup | 6.3.9600.23398 |
| Windows Server 2012 R2 | KB5123066 · Monthly Rollup | 6.3.9600.23398 |
| Windows Server 2012 (Server Core installation) | KB5123065 · Monthly Rollup | 6.2.9200.26349 |
| Windows Server 2012 | KB5123065 · Monthly Rollup | 6.2.9200.26349 |
| Windows Server 2016 (Server Core installation) | KB5123099 · Security Update | 10.0.14393.9512 |
| Windows Server 2016 | KB5123099 · Security Update | 10.0.14393.9512 |
| Windows 10 Version 1607 for x64-based Systems | KB5123099 · Security Update | 10.0.14393.9512 |
| Windows 11 Version 26H1 for ARM64-based Systems | KB5124012 · Security Update | 10.0.28000.2954 |
| Windows 10 Version 1607 for 32-bit Systems | KB5123099 · Security Update | 10.0.14393.9512 |
| Windows 11 version 26H1 for x64-based Systems | KB5124012 · Security Update | 10.0.28000.2954 |
| Windows 11 Version 24H2 for x64-based Systems | KB5124008 · Security Update | 10.0.26100.9445 |
| Windows Server 2025 | KB5122871 · Security Update | 10.0.26100.33438 |
| Windows 11 Version 24H2 for ARM64-based Systems | KB5124008 · Security Update | 10.0.26100.9445 |
| Windows 11 Version 23H2 for x64-based Systems | KB5122880 · Security Update | 10.0.22631.7582 |
| Windows 11 Version 23H2 for ARM64-based Systems | KB5122880 · Security Update | 10.0.22631.7582 |
| Windows 11 Version 25H2 for ARM64-based Systems | KB5124008 · Security Update | 10.0.26200.9445 |
| Windows 11 Version 25H2 for x64-based Systems | KB5124008 · Security Update | 10.0.26200.9445 |
| Windows Server 2025 (Server Core installation) | KB5122871 · Security Update | 10.0.26100.33438 |
| Windows 10 Version 22H2 for 32-bit Systems | KB5122878 · Security Update | 10.0.19045.7725 |
| Windows 10 Version 22H2 for ARM64-based Systems | KB5122878 · Security Update | 10.0.19045.7725 |
| Windows 10 Version 21H2 for ARM64-based Systems | KB5122878 · Security Update | 10.0.19044.7725 |
| Windows 10 Version 22H2 for x64-based Systems | KB5122878 · Security Update | 10.0.19045.7725 |
| Windows 10 Version 21H2 for 32-bit Systems | KB5122878 · Security Update | 10.0.19044.7725 |
| Windows Server 2022 (Server Core installation) | KB5122882 · Security Update | 10.0.20348.5622 |
| Windows 10 Version 21H2 for x64-based Systems | KB5122878 · Security Update | 10.0.19044.7725 |
| Windows Server 2022 | KB5122882 · Security Update | 10.0.20348.5622 |
| Windows Server 2019 (Server Core installation) | KB5122876 · Security Update | 10.0.17763.9245 |
| Windows 10 Version 1809 for 32-bit Systems | KB5122876 · Security Update | 10.0.17763.9245 |
| Windows 10 Version 1809 for x64-based Systems | KB5122876 · Security Update | 10.0.17763.9245 |
| Windows Server 2019 | KB5122876 · Security Update | 10.0.17763.9245 |
FAQ
- What type of information could be disclosed by this vulnerability?
- An attacker who successfully exploited this vulnerability could view heap memory from a privileged process running on the server.
Revisions
| Version | Date | Note |
|---|---|---|
| 1 | 8 sep 2026 | Information published. |
This is in the weekly digest for week 37 · What changed this week? →
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Source: Microsoft Security Update Guide. 365Fanatic is not affiliated with Microsoft.
