CVE-2026-55021: Microsoft SharePoint Server Spoofing Vulnerability

highCVSS 7.3CVE-2026-55021

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.

CSIRTS triage

vendor: Microsoft product: SharePoint Server Cross-site scripting

What: 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.
Who is affected: Users of Microsoft Office SharePoint.
Urgency: Remediation is urgent due to the high severity of the spoofing vulnerability.
Action: Apply the latest security updates for SharePoint Server.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 7.3
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55021

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-550210.65% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 48% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-55021	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

unknownexploitedNCSC-2026-0237 [1.02] [H/H] Vulnerabilities Fixed in Microsoft Officencsc-nl
unknownexploitedNCSC-2026-0237 [1.01] [H/H] Vulnerabilities fixed in Microsoft Officencsc-nl
unknownMultiple vulnerabilities in Microsoft products (July 15, 2026)cert-fr-avis
unknownexploitedNCSC-2026-0237 [1.00] [M/H] Vulnerabilities fixed in Microsoft Officencsc-nl
highCVE-2026-55021: Improper neutralization of input during web page generation ('cross-site scripting') in Micros…nvd