Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:N) | Network: reachable remotely |
| Attack complexity (AC:L) | Low complexity |
| Privileges required (PR:L) | Low privileges required |
| User interaction (UI:R) | A user must take an action |
| Scope (S:U) | Scope unchanged |
| Confidentiality (C:H) | High confidentiality impact |
| Integrity (I:H) | High integrity impact |
| Availability (A:N) | No availability impact |
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N
About Microsoft Sharepoint Server
CVE-2026-55034 affects Microsoft Sharepoint Server, a product from Microsoft. Before acting, confirm where Microsoft Sharepoint Server runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Office SharePoint allows an authorized attacker to perform spoofing over a network.
The weakness class is Cross Site Scripting. Attacker supplied script runs in another user's browser inside the trusted site.
Based on its CVSS vector, the flaw can be reached over the network, needs some level of access, and relies on a user taking an action. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | Microsoft Sharepoint Server |
| Affected versions | Sharepoint Server before 16.0.19725.20434; Sharepoint Server 2016; Sharepoint Server 2019 |
| Published | Jul 14, 2026 |
| Last modified | Jul 15, 2026 |
| Added to CISA KEV | Not listed |
| Assigning CNA | secure@microsoft.com |
How to detect it
- Inventory every instance of Microsoft Sharepoint Server and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of Microsoft Sharepoint Server named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on Microsoft Sharepoint Server to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Rank using EPSS and CVSS together with asset exposure and business impact. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
- CWE-79: Cross Site Scripting More CVEs with this weakness
Technical References
Frequently asked questions
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