A VULNERABILITY RELATED to Amazon Web Service’s traffic-routing service known as Application Load Balancer could have been exploited by an attacker to bypass access controls and compromise web applications, according to new research. The flaw stems from a customer implementation issue, meaning it isn’t caused by a software bug. Instead, the exposure was introduced by the way AWS users set up authentication with Application Load Balancer.

Implementation issues are a crucial component of cloud security in the same way that the contents of an armored safe aren’t protected if the door is left ajar. Researchers from the security firm Miggo found that, depending on how Application Load Balancer authentication was set up, an attacker could potentially manipulate its hand-off to a third-party corporate authentication service to access the target web application and view or exfiltrate data.

The researchers say that looking at publicly reachable web applications, they have identified more than 15,000 that appear to have vulnerable configurations. AWS disputes this estimate, though, and says that “a small fraction of a percent of AWS customers have applications potentially badly configured in this way, significantly fewer than the researchers’ estimate.” The company also says that it has contacted each customer on its shorter list to recommend a more secure implementation. AWS does not have access or visibility into its clients’ cloud environments, though, so any exact number is just an estimate.

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