#VU53877 Code Injection in Microsoft SharePoint Server and Microsoft SharePoint Foundation - CVE-2021-26420

Vulnerability identifier: #VU53877

Vulnerability risk: Medium

CVSSv4.0: 5.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-26420

CWE-ID: CWE-94

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Microsoft SharePoint Server
Server applications / Application servers
Microsoft SharePoint Foundation
Server applications / Application servers

Vendor: Microsoft

Description

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

The vulnerability exists due to improper input validation within the System.Workflow.ComponentModel.Compiler.WorkflowCompilerInternal class in the Microsoft SharePoint Server. A remote authenticated attacker can send a specially crafted request and execute arbitrary code on the target system.

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

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Microsoft SharePoint Server: 2016 - 2019

Microsoft SharePoint Foundation: 2013

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External links
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26420
https://www.zerodayinitiative.com/advisories/ZDI-21-755/

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.