Threat Response: Critical Vulnerability in Microsoft XML deserialisation



Last week (July 14th) we sent out a notice about patches Microsoft released, among which a critical vulnerability in Windows DNS Server. Over the last few days details have emerged on another critical vulnerability that has been fixed in the same round of updates. This vulnerability is related to the way XML is deserialised and is present in several Microsoft products, namely the .Net Framework, Sharepoint and Visual Studio. As the .Net Framework is affected, many products that use this framework might also be at risk. The vulnerability is filed under CVE-2020-1147[1] and has received a CVSS score of 9.8. At the time of writing there is no known public exploit available, however many details are being posted [2] that simplify the development of an exploit. In this message we inform you of the threat and potential mitigations.

As the .Net Framework is also affected, there can also be risks to Linux systems that have .Net Core installed. Several Linux distributions have made patches available, some examples:  [3] [4].


This vulnerability allows for arbitrary code execution on the affected systems. The code will have the same privileges as the process performing the xml deserialisation. This makes the impact high.


There is no public or active exploit available. As lots of detailed information has been publicised that simplifies exploit development, it is expected that public/active exploits will follow soon. Northwave assesses the risk of this vulnerability to be high.


Northwave repeats the recommendation to install the patches released last week as soon as possible. This recommendation has gained more weight with this additional vulnerability. Additionally, there are no known alternative mitigations or work arounds for this issue.

Lastly, non-Windows systems that have .Net Core installed should be updated as soon as possible.

Northwave will monitor any developments regarding this vulnerability. If new critical information about this threat arises, we will reach out to you. If you need additional information you can call us by phone or send us an email.

E-mail: [email protected]
Do you have an incident right now? Call our CERT number: +31 (0)85 043 7909 or 0800-1744 (alleen vanuit Nederland)

Disclaimer applies, see below.






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