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Microsoft Azure Flaws Exposed RHEL Instances

Vulnerabilities in Microsoft’s Azure cloud platform could have been exploited by attackers to gain administrator access to Red Hat Enterprise Linux (RHEL) instances and storage accounts, according to a software engineer.

Azure and Amazon Web Services (AWS) rely on the Red Hat Update Infrastructure (RHUI) to manage yum repository content for RHEL instances. Red Hat Update Appliances, which contact the Red Hat Network to fetch new and updated packages, have been created by Microsoft and Amazon for each region.

While trying to create a RHEL image that could be used on both Azure and AWS, Irish researcher Ian Duffy noticed that some Red Hat Package Manager (RPM) files contained client configurations for each region. This allowed the discovery of all Red Hat Update Appliances, with all servers exposing their REST APIs over HTTPS.

An application running on port 8080 revealed the locations of archives containing logs and configuration files. The archives included SSL certificates that could be used to gain full administrative access to Red Hat Update Appliances.

Full access to an appliance’s REST API and the lack of package signature checks allowed an attacker to upload packages that would be acquired by client virtual machines when performing a yum update. With the yum update installed, the attacker may have been able to gain root access to all virtual machines that executed the update.

In addition to data stored in virtual machines, an attacker might have been able to obtain access to storage accounts.

“Given some poor implementation within the mandatory Microsoft Azure Linux Agent (WaLinuxAgent), one is able to obtain the administrator API keys to the storage account used by the virtual machine for debug log shipping purposes. At the time of research, this storage account defaulted to one shared by multiple virtual machines,” Duffy said. “If the storage account was used by multiple virtual machines there is potential to download their virtual hard disks.”

The flaws were reported to Microsoft through the company’s bug bounty program. The tech giant confirmed the issues and took steps to prevent public access to the app on port 8080 and Red Hat Update Appliances.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.