CVE-2026-123383: Microsoft Office Outlook Remote Code Execution Vulnerability
CVE-2026-123383 is a remote code execution vulnerability in Microsoft Office Outlook, rated Important by Microsoft, with a CVSS 3.1 base score of 8.8 (High). An attacker can exploit it remotely over the network, without any privileges and only if a user takes an action. Microsoft has not reported exploitation in the wild and rates exploitation as less likely. Microsoft released the fix on 10 November 2026 in the November 2026 Patch Tuesday. It affects 6 products in 1 product family (Microsoft Office).
Key facts
- CVE ID
- CVE-2026-123383
- Severity
- High CVSS 8.8
- Microsoft severity
- Important
- Impact
- Remote Code Execution
- Exploited in the wild
- No
- Publicly disclosed
- No
- Exploitation likelihood
- Less Likely
- Weakness
- CWE-122
- CISA KEV
- Not listed
- Released
- Last updated
- Patch Tuesday
- November 2026 Patch Tuesday
- Product families
- Microsoft Office
CVSS score and vector
Microsoft scores CVE-2026-123383 at 8.8 (temporal 7.7) using CVSS 3.1. Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
| Metric | Value |
|---|---|
| Attack vector | Network |
| Attack complexity | Low |
| Privileges required | None |
| User interaction | Required |
| Scope | Unchanged |
| Confidentiality impact | High |
| Integrity impact | High |
| Availability impact | High |
| Exploit code maturity | Unproven |
| Remediation level | Official fix |
| Report confidence | Confirmed |
Description
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.
Frequently asked questions (Microsoft)
Is the Preview Pane an attack vector for this vulnerability?
No, the Preview Pane is not an attack vector.
How could an attacker exploit this vulnerability?
An attacker could send a specially crafted email and convince a user to copy its attachment in Outlook. When the copied attachment is processed by another application, successful exploitation could allow code execution with the user's privileges.
Affected products (6)
Microsoft Office
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| Microsoft Office LTSC 2021 for 64-bit editions | Release Notes | Security Update | 16.0.14334.21048 | |
| Microsoft Office LTSC 2021 for 32-bit editions | Release Notes | Security Update | 16.0.14334.21048 | |
| Microsoft Office LTSC 2024 for 64-bit editions | Release Notes | Security Update | 16.0.17932.21140 | |
| Microsoft Office LTSC 2024 for 32-bit editions | Release Notes | Security Update | 16.0.17932.21140 | |
| Microsoft 365 Apps for Enterprise for 64-bit Systems | Release Notes | Security Update | https://aka.ms/OfficeSecurityReleases | |
| Microsoft 365 Apps for Enterprise for 32-bit Systems | Release Notes | Security Update | https://aka.ms/OfficeSecurityReleases |
NIST NVD data
- NVD status
- Awaiting Analysis
- NVD CVSS
- 8.8 (HIGH)
- NVD weakness
- CWE-122
- Published to NVD
- NVD last modified
References
Acknowledgments
Revision history
| Version | Date | Description |
|---|---|---|
| 1.0 | Information published. |