Microsoft .NET Framework up to 4.8 XML File code injection

Summaryinfo

A vulnerability described as critical has been identified in Microsoft .NET Framework up to 4.8. This issue affects some unknown processing of the component XML File Handler. Executing a manipulation can lead to code injection. This vulnerability is handled as CVE-2020-1147. The attack can be executed remotely. Additionally, an exploit exists. It is advisable to implement a patch to correct this issue.

Detailsinfo

A vulnerability was found in Microsoft .NET Framework up to 4.8 (Programming Language Software). It has been declared as critical. This vulnerability affects an unknown code block of the component XML File Handler. The manipulation with an unknown input leads to a code injection vulnerability. The CWE definition for the vulnerability is CWE-94. The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

A remote code execution vulnerability exists in .NET Framework, Microsoft SharePoint, and Visual Studio when the software fails to check the source markup of XML file input, aka '.NET Framework, SharePoint Server, and Visual Studio Remote Code Execution Vulnerability'.

The weakness was released 07/14/2020 as confirmed security update guide (Website). The advisory is shared for download at portal.msrc.microsoft.com. The public release was coordinated with the vendor. This vulnerability was named CVE-2020-1147. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details are unknown but a public exploit is available. The MITRE ATT&CK project declares the attack technique as T1059. The advisory points out:

A remote code execution vulnerability exists in .NET Framework, Microsoft SharePoint, and Visual Studio when the software fails to check the source markup of XML file input. An attacker who successfully exploited the vulnerability could run arbitrary code in the context of the process responsible for deserialization of the XML content.

A public exploit has been developed by West Shepherd in Python and been published 2 months after the advisory. It is possible to download the exploit at exploit-db.com. It is declared as attacked. As 0-day the estimated underground price was around $5k-$25k. This issue was added on 11/03/2021 to the CISA Known Exploited Vulnerabilities Catalog with a due date of 05/03/2022:

Apply updates per vendor instructions.

Applying a patch is able to eliminate this problem. A possible mitigation has been published immediately after the disclosure of the vulnerability.

The vulnerability is also documented in the vulnerability database at Exploit-DB (48747). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• Programming Language Software

Vendor

• Microsoft

Name

• .NET Framework

Version

• 2.0 SP2
• 3.0 SP2
• 3.5
• 3.5.1
• 4.5.2
• 4.6
• 4.6.1
• 4.6.2
• 4.7
• 4.7.1
• 4.7.2
• 4.8

License

• free

Website

• Vendor: https://www.microsoft.com/

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Once again VulDB remains the best source for vulnerability data.

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