CVE-2026-70321: Microsoft SharePoint Remote Code Execution Vulnerability
CVE-2026-70321 is a remote code execution vulnerability in Microsoft SharePoint, rated Important by Microsoft, with a CVSS 3.1 base score of 8.8 (High). An attacker can exploit it remotely over the network, with low privileges and without user interaction. Microsoft has not reported exploitation in the wild and rates exploitation as less likely. The EPSS model estimates a 1.69% probability of exploitation activity in the next 30 days, higher than 77% of all scored vulnerabilities. Microsoft released the fix on 11 August 2026 in the August 2026 Patch Tuesday, delivered through 1 security update (KB5002893). It affects 1 product in 1 product family (Microsoft Office).
Key facts
- CVE ID
- CVE-2026-70321
- 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-502
- EPSS
- 1.69% (percentile 77%)
- CISA KEV
- Not listed
- Released
- Last updated
- Patch Tuesday
- August 2026 Patch Tuesday
- Product families
- Microsoft Office
CVSS score and vector
Microsoft scores CVE-2026-70321 at 8.8 (temporal 7.7) using CVSS 3.1. Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
| Metric | Value |
|---|---|
| Attack vector | Network |
| Attack complexity | Low |
| Privileges required | Low |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality impact | High |
| Integrity impact | High |
| Availability impact | High |
| Exploit code maturity | Unproven |
| Remediation level | Official fix |
| Report confidence | Confirmed |
Description
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
Frequently asked questions (Microsoft)
How could an attacker exploit this vulnerability?
Successful exploitation of this vulnerability could allow an attacker the ability to gain remote code execution via an in-network attacker calling arbitrary endpoints.
Affected products (1)
Microsoft Office
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| Microsoft SharePoint Server Subscription Edition | KB5002893 | Security Update | 16.0.19725.20522 | Maybe |
Security updates (1)
- KB5002893 (Security Update)
NIST NVD data
- NVD status
- Analyzed
- NVD CVSS
- 8.8 (HIGH)
- NVD weakness
- CWE-502
- Published to NVD
- NVD last modified
Affected configurations (CPE)
| Product | Vulnerable versions |
|---|---|
| sharepoint server | before 16.0.19725.20522 |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-70321 (Vendor Advisory, Patch)
Acknowledgments
- Kn1ght
Revision history
| Version | Date | Description |
|---|---|---|
| 1.0 | Information published. |