Microsoft seems to have had a slight change of heart when it comes to the security risk its Azure Service Tags are posing.
While initially claiming the tool was never meant to be a security measure, the company is now warning users that there are scenarios in which Service Tags could be used to gain unauthorized access to cloud resources.
Microsoft did stress that such scenarios were not yet observed in the wild and that there is no evidence of abuse in the real world (yet).
Not a security boundary
Earlier in 2024, cybersecurity researchers from Tenable claimed Azure Service Tags were vulnerable to a flaw that could let threat actors steal people’s sensitive data. Service Tags is a feature that helps simplify network security management by allowing users to define network access controls based on logical groups of IP addresses rather than individual IP addresses. These service tags represent a group of IP address prefixes from specific Azure services, which can be used in security rules for network security groups (NSGs), user-defined routes (UDRs), and Azure Firewall.
Tenable said that the tool could be used to craft malicious SSRF-like web requests and thus pose as trusted Azure services. Hence, any firewall rules based on Azure Service Tags are rendered moot.
At the time, Microsoft stressed that Service Tags are “not to be treated as a security boundary and should only be used as a routing mechanism in conjunction with validation controls.”
In an “Improved Guidance for Azure Network Service Tags” document, posted on the Microsoft website earlier this month, it doubled down on this assessment, but warned that some risk exists:
“Microsoft Security Response Center (MSRC) was notified in January 2024 by our industry partner, Tenable Inc., about the potential for cross-tenant access to web resources using the service tags feature. Microsoft acknowledged that Tenable provided a valuable contribution to the Azure community by highlighting that it can be easily misunderstood how to use service tags and their intended purpose,” Microsoft said.
“Cross-tenant access is prevented by authentication and only represents an issue where authentication is not used. However, this case does highlight an inherent risk in using service tags as a single mechanism for vetting incoming network traffic.”
The goal of the Improved Guidance, Redmond added, was to help businesses better understand service tags and how they function, and not to warn about any flaws in the design:
“As always, we strongly encourage customers to use multiple layers of security for their resources,” Microsoft stressed. “There is no mandatory action required by customers and no additional messaging provided in the Azure Portal. However, Microsoft strongly recommends that customers proactively review their use of service tags and validate their security measures to authenticate only trusted network traffic for service tags.”
Via TheHackerNews
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