Microsoft addressed critical flaw in Windows Host Compute Service Shim library

Microsoft released an out of band update to address a critical remote code execution vulnerability in the Windows Host Compute Service Shim library (hcsshim).

Microsoft announced that it has issued a security update to address a critical remote code execution vulnerability in the Windows Host Compute Service Shim library (hcsshim).

The Windows Host Compute Service (HCS) is a low-level container management API in Hyper-V, Microsoft implemented two open source wrappers to invoke HCS functions using higher level programming languages.

The Windows Host Compute Service Shim wrapper, introduced in January 2017, allows the launch of Windows Server containers from the Go language.

“We’ve released two wrappers thus far. One is written in Go (and used by Docker), and the other is written in C#.” reads a blog post published by Microsoft.

“You can find the wrappers here:

The security expert Michael Hanselmann discovered that hcsshim fails to properly validate input when importing a container image, the vulnerability, tracked as CVE-2018-8115, could be exploited by a remote attacker to execute arbitrary code on the host operating system.

“A remote code execution vulnerability exists when the Windows Host Compute Service Shim (hcsshim) library fails to properly validate input while importing a container image.” reads the security advisory published by Microsoft.

“To exploit the vulnerability, an attacker would place malicious code in a specially crafted container image which, if an authenticated administrator imported (pulled), could cause a container management service utilizing the Host Compute Service Shim library to execute malicious code on the Windows host.”

While US-CERT has released an alert urging to update the library, Microsoft tried to downplay the problem explaining that it is unlikely that the flaw could be exploited in attacks in the wild.

Microsoft addressed the vulnerability with the out-of-band update hcsshim 0.6.10 that is available on GitHub.

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Pierluigi Paganini

(Security Affairs – Windows Host Compute Service Shim library, hacking)

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Pierluigi Paganini

Pierluigi Paganini is member of the ENISA (European Union Agency for Network and Information Security) Threat Landscape Stakeholder Group and Cyber G7 Group, he is also a Security Evangelist, Security Analyst and Freelance Writer. Editor-in-Chief at "Cyber Defense Magazine", Pierluigi is a cyber security expert with over 20 years experience in the field, he is Certified Ethical Hacker at EC Council in London. The passion for writing and a strong belief that security is founded on sharing and awareness led Pierluigi to find the security blog "Security Affairs" recently named a Top National Security Resource for US. Pierluigi is a member of the "The Hacker News" team and he is a writer for some major publications in the field such as Cyber War Zone, ICTTF, Infosec Island, Infosec Institute, The Hacker News Magazine and for many other Security magazines. Author of the Books "The Deep Dark Web" and “Digital Virtual Currency and Bitcoin”.