CVE-2026-55126Network attack vector

Authenticated spoofing via multiline-field script injection

Published Jul 14, 2026 · Updated Jul 14, 2026

Cross-site scripting in affected Microsoft SharePoint Server releases allows remote authenticated users to execute script as a target user. The SPFieldMultiLineText class fails to validate user-supplied data before page generation, allowing arbitrary script injection. Exploitation requires SharePoint authorization and a target to visit a malicious page or open a malicious file; injected script can issue web requests with that target's privileges.

CVSS severity7.3
High
EPSS probability0.65%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in affected Microsoft SharePoint Server releases allows remote authenticated users to execute script as a target user. The SPFieldMultiLineText class fails to validate user-supplied data before page generation, allowing arbitrary script injection. Exploitation requires SharePoint authorization and a target to visit a malicious page or open a malicious file; injected script can issue web requests with that target's privileges.

The record

CVE
CVE-2026-55126
Published
Jul 14, 2026
Updated
Jul 14, 2026
Vendor
Microsoft
Product
Microsoft SharePoint Enterprise Server 2016
Classifications
CWE-79
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=16.0.0 <16.0.5561.1001

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Microsoft · Microsoft SharePoint Enterprise Server 2016version=16.0.0 <16.0.5561.1001
Microsoft · Microsoft SharePoint Server 2019version=16.0.0 <16.0.10417.20175
Microsoft · Microsoft SharePoint Server Subscription Editionversion=16.0.0 <16.0.19725.20434

Published CVSS scores

5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
7.3Microsoft CorporationCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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