CVE-2026-33110: Microsoft SharePoint Server Remote Code Execution Vulnerability
CVE-2026-33110 is a remote code execution vulnerability in Microsoft SharePoint Server, 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 1.97% probability of exploitation activity in the next 30 days, higher than 81% of all scored vulnerabilities. Microsoft released the fix on 12 May 2026 in the May 2026 Patch Tuesday, delivered through 3 security updates (KB5002868, KB5002870, KB5002863). It affects 3 products in 1 product family (Microsoft Office).
Key facts
- CVE ID
- CVE-2026-33110
- 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
- 1.97% (percentile 81%)
- CISA KEV
- Not listed
- Released
- Last updated
- Patch Tuesday
- May 2026 Patch Tuesday
- Product families
- Microsoft Office
CVSS score and vector
Microsoft scores CVE-2026-33110 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)
I am running SharePoint Server 2016. Do the updates for SharePoint Enterprise Server 2016 also apply to the version I am running?
Yes. The same KB number applies to both SharePoint Server 2016 and SharePoint Enterprise Server 2016. Customers running either version should install the security update to be protected from this vulnerability.
According to the CVSS metric, privileges required is low (PR:L). What does that mean for this vulnerability?
Any authenticated attacker could trigger this vulnerability. It does not require admin or other elevated privileges.
How could an attacker exploit the vulnerability?
In a network-based attack, an authenticated attacker, who has a minimum of Site Member permissions (PR:L), could execute code remotely on the SharePoint Server.
According to the CVSS metric, the attack vector is network (AV:N) and the attack complexity is low (AC:L). What does that mean for this vulnerability?
The attack vector is Network (AV:N) because this vulnerability is remotely exploitable and can be exploited from the internet. The attack complexity is Low (AC:L) because an attacker does not require significant prior knowledge of the system and can achieve repeatable success with the payload against the vulnerable component.
Affected products (3)
Microsoft Office
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| Microsoft SharePoint Enterprise Server 2016 | KB5002868 | Security Update | 16.0.5552.1002 | Maybe |
| Microsoft SharePoint Server 2019 | KB5002870 | Security Update | 16.0.10417.20128 | Maybe |
| Microsoft SharePoint Server Subscription Edition | KB5002863 | Security Update | 16.0.19725.20280 | Maybe |
Security updates (3)
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 16.0.19725.20280 |
| sharepoint server 2016 | all listed versions |
| sharepoint server 2019 | all listed versions |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-33110 (Vendor Advisory)
Acknowledgments
- f7d8c52bec79e42795cf15888b85cbad
Revision history
| Version | Date | Description |
|---|---|---|
| 1.0 | Information published. |