Microsoft SharePoint Code Injection
CVE-2026-65660 is a high-severity improper control of generation of code vulnerability in Microsoft SharePoint Enterprise Server 2016 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 attacker with a low-privileged account, without any action from a user. The record lists version 16.0.5565.1001 as the first without the flaw, so updating Microsoft SharePoint Enterprise Server 2016 to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on September 25, 2026, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Microsoft SharePoint Enterprise Server 2016 to 16.0.5565.1001 or a later version.
- Update Microsoft SharePoint Server 2019 to 16.0.10417.20198 or a later version.
- Update Microsoft SharePoint Server Subscription Edition to 16.0.19725.20522 or a later version.
- CISA's required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
- Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Microsoft | Microsoft SharePoint Enterprise Server 2016 | 16.0.0 up to, but not including, 16.0.5565.1001 | 16.0.5565.1001 |
| Microsoft | Microsoft SharePoint Server 2019 | 16.0.0 up to, but not including, 16.0.10417.20198 | 16.0.10417.20198 |
| Microsoft | Microsoft SharePoint Server Subscription Edition | 16.0.0 up to, but not including, 16.0.19725.20522 | 16.0.19725.20522 |
| Microsoft | Sharepoint Server | before 16.0.19725.20522; 2016; 2019 | 16.0.19725.20522 |
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
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- 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:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (microsoft.com).
Official description
Improper control of generation of code ('code injection') in Microsoft Office SharePoint allows an authorized 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: Improper Control of Generation of Code
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.
How developers prevent this class of flaw
- Refactor your program so that you do not have to dynamically generate code.
- Run your code in a jail or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which code can be executed by your product. Examples include the Unix chroot jail and AppArmor. In general, managed code may provide some protection. This may not be a feasible solution, and it only limits the impact to the operating system; the rest of your application may still be subject to compromise. Be careful to avoid CWE-243 and other weaknesses related to jails.
- Use dynamic tools and techniques that interact with the product using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The product's operation may slow down, but it should not become unstable, crash, or generate incorrect results.
More Improper Control of Generation of Code vulnerabilities (CWE-94)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
Other vulnerabilities in Microsoft SharePoint Enterprise Server 2016
- 9.3 Critical severity
Recent Improper Control of Generation of Code vulnerabilities
- 8.5 High severity
- 7.8 High severity
- 7.8 High severity
- 9.4 Critical severity
- 8.5 High severity
- 9.6 Critical severity
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