EUVD-2026-44166
GHSA-c9qw-72v3-rp2r
Severity by source
AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
Network-reachable stored XSS needing an authenticated low-priv account (PR:L) and victim viewing (UI:R); script escapes into the victim's trusted origin (S:C) with high C/I and no availability impact.
Primary rating from Vendor (microsoft).
CVSS VectorNVD
Lifecycle Timeline
5DescriptionNVD
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.
AnalysisAI
Spoofing via stored cross-site scripting in Microsoft SharePoint (Enterprise Server 2016, Server 2019, and Subscription Edition) allows an authenticated attacker to inject script that executes in another user's browser session across a network. CVSS is 8.7 with a scope change, reflecting that injected content escapes into the victim's authenticated context; there is no public exploit identified at time of analysis and CISA SSVC rates exploitation status as none. A vendor patch is available via Microsoft MSRC.
Technical ContextAI
The flaw is a CWE-79 (improper neutralization of input during web page generation) issue in SharePoint's server-side rendering of user-supplied content. SharePoint is Microsoft's on-premises collaboration and document management platform, and affected editions per CPE are microsoft_sharepoint_enterprise_server_2016, microsoft_sharepoint_server_2019, and microsoft_sharepoint_server_subscription_edition. Because SharePoint stores and re-renders user-authored content (lists, pages, web parts, metadata) to other users, insufficient output encoding lets attacker-controlled markup persist and later execute as script in a victim's browser within the trusted SharePoint origin - the classic stored/persistent XSS pattern that Microsoft categorizes here as a network spoofing impact.
RemediationAI
Apply the Microsoft security update referenced in the MSRC advisory (https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55021), upgrading to the fixed builds: SharePoint Enterprise Server 2016 to 16.0.5561.1001 or later, SharePoint Server 2019 to 16.0.10417.20175 or later, and SharePoint Server Subscription Edition to 16.0.19725.20434 or later (Vendor-released patch confirmed available per vendor advisory). Until patching, reduce exposure by restricting who can author or contribute content to sites (limit contribute/edit permissions to trusted users, since exploitation requires an authenticated low-privilege account), and consider fronting SharePoint with a WAF tuned to strip or encode script payloads in stored fields - noting a WAF may cause false positives on legitimate rich content and is not a substitute for the update. Avoid exposing SharePoint web front-ends directly to the internet where feasible; the trade-off is reduced external collaboration convenience.
Remote code execution in Microsoft SharePoint Server (2016, 2019, and Subscription Edition) lets an unauthenticated atta
Remote code execution in Microsoft SharePoint (Enterprise Server 2016, Server 2019, and Server Subscription Edition) all
Security feature bypass in Microsoft SharePoint (Enterprise Server 2016, Server 2019, and Server Subscription Edition) l
Privilege elevation in Microsoft SharePoint Server (Enterprise Server 2016, Server 2019, and Subscription Edition) lets
Authenticated remote code execution in Microsoft SharePoint (Enterprise Server 2016, Server 2019, and Subscription Editi
Privilege elevation in Microsoft SharePoint Server (Enterprise Server 2016 and Server 2019) allows an authenticated netw
Privilege escalation in Microsoft SharePoint Server (Enterprise Server 2016, Server 2019, and Subscription Edition) lets
Cross-site scripting (CWE-79) in on-premises Microsoft SharePoint Server allows an authenticated, low-privileged attacke
Local code execution in Microsoft Word (and Office/SharePoint components that render Word content) stems from an integer
Arbitrary code execution in Microsoft Office Word (and the broader Office/365/SharePoint family) arises from a stack-bas
Local code execution in Microsoft Word (part of Microsoft 365 Apps, Office 2019, Office LTSC 2021/2024, and Office for M
Local code execution in Microsoft Word (and the wider Microsoft Office / Microsoft 365 Apps family) lets an unauthorized
Same weakness CWE-79 – Cross-site Scripting (XSS)
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External POC / Exploit Code
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