SB2026031107 - Multiple vulnerabilities in Microsoft SharePoint Server

Description

This security bulletin contains information about 3 vulnerabilities.

1) Input validation error (CVE-ID: CVE-2026-26106)

CWE-ID: CWE-20 - Improper input validation

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote attacker to execute arbitrary code on the system.

The vulnerability exists due to insufficient validation of user-supplied input in Microsoft SharePoint Server. A remote user can pass specially crafted input to the application and execute arbitrary code on the target system.

2) Cross-site scripting (CVE-ID: CVE-2026-26105)

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

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U/U:Clear

The disclosed vulnerability allows a remote attacker to perform cross-site scripting (XSS) attacks.

The vulnerability exists due to insufficient sanitization of user-supplied data in v. A remote attacker can trick the victim to follow a specially crafted link and execute arbitrary HTML and script code in user's browser in context of vulnerable website.

Successful exploitation of this vulnerability may allow a remote attacker to steal potentially sensitive information, change appearance of the web page, perform phishing and drive-by-download attacks.

3) Deserialization of Untrusted Data (CVE-ID: CVE-2026-26114)

CWE-ID: CWE-502 - Deserialization of Untrusted Data

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to insecure input validation when processing serialized data in Microsoft SharePoint Server. A remote user can pass specially crafted data to the application and execute arbitrary code on the target system.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.

Remediation

Install update from vendor's website.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26106
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26105
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26114