Azurescape VULNERABILITY ALLOWS Cross Account Takeover in Container Instances

Azure Container Instances (ACI) is Azure's Container-as-a-Service (CaaS) offering, enabling customers to run containers on Azure without managing the underlying servers. Unit 42 security researchers recently identified and disclosed critical security issues in ACI to Microsoft. A malicious Azure user could have exploited these issues to execute code on other users' containers, steal customer secrets and images deployed to the platform, and possibly abuse ACI's infrastructure for cryptomining. Researchers named the vulnerability “Azurescape” – the first cross-account container takeover in the public cloud.

Azurescape allowed malicious users to compromise the multitenant Kubernetes clusters hosting ACI, establishing full control over other users' containers. In summary, the Azurescape exploit worked like this, as demonstrated in this YouTube video:

• Deploy an image exploiting CVE-2019-5736 to ACI. The malicious image breaks out upon execution and establishes code execution on the underlying node;
• On the node, monitor traffic on the Kubelet port, port 10250, and wait for a request that includes a JWT token in the Authorization header;
• Issue “az container” exec command to run a command on the uploaded container. The bridge pod will now send an exec request to the Kubelet on the compromised node; and
• On the node, extract the bridge token from the request’s Authorization header and use it to open a shell on the API server.

Microsoft has patched ACI shortly after the vulnerability disclosure. There are no security alerts or knowledge of Azurescape exploited in the wild. As a precautionary measure, if you run containers on ACI, we recommend revoking any privileged credentials that were deployed to the platform before Aug. 31, 2021, and checking their access logs for any irregularities.

The rapid acceleration of the shift to the cloud that has occurred in the past few years has made these platforms a prized target for malicious actors. While we’ve long been focused on identifying new cloud threats, discovery of the first cross-account container takeover underscores the importance of that effort. Sophisticated attackers may not be satisfied with targeting end users, and may expand their campaigns to the platforms themselves to increase impact and reach.

​The best way to prevent cyber attacks on any cloud environment is to implement a comprehensive cloud native security platform such as Prisma Cloud, which is able to detect and mitigate malicious behaviour as well as identify vulnerabilities in cloud environments. Contact us to learn how we can secure your infrastructure, applications and data across hybrid and multi-cloud environments.

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