Amazon Web Services (AWS) has addressed a significant cross-tenant vulnerability within its platform that could allow unauthorized access to resources. This issue, characterized as a “confused deputy problem,” pertains to a form of privilege escalation where an entity lacking permissions can manipulate a more privileged entity into performing actions on its behalf.
The vulnerability was initially reported by Datadog on September 1, 2022, and a patch was swiftly released on September 6. According to Datadog researcher Nick Frichette, the exploit involved the AWS AppSync service to assume identity and access management roles in other AWS accounts, enabling potential attackers to penetrate organizations and access sensitive resources within these accounts.
In a coordinated disclosure, AWS clarified that only minor issues persisted, asserting that no customers were affected and no immediate actions were required on their part. The company described the flaw as a “case-sensitivity parsing issue” within AWS AppSync, which could potentially bypass cross-account validation measures, granting actions ostensibly permissible by the service across different customer accounts.
AWS AppSync serves as a robust platform enabling developers to create GraphQL APIs that facilitate data retrieval from multiple sources and synchronize information across mobile, web applications, and the cloud. Moreover, it provides integration capabilities with other AWS services, employing specific roles to execute necessary API calls with designated IAM permissions.
Despite built-in safeguards aimed at preventing AppSync from assuming arbitrary roles by authenticating the role’s unique Amazon Resource Name (ARN), the identified issue arose from the ability to sidestep this check by using the “serviceRoleArn” parameter in lowercase. This breach of ARN validation could allow attackers to specify a role from a different AWS account, thus facilitating unauthorized interaction with various resources.
Frivette emphasized the severity of this vulnerability, noting that it enabled attackers to cross between account boundaries and leverage AWS API calls in victim accounts via IAM roles linked to the AppSync service. This method of attack presented a significant risk to organizations utilizing AppSync, as it provided a pathway for hostile actors to breach security measures and access critical resources associated with the compromised roles.
From a cybersecurity perspective, this incident falls within several tactics and techniques outlined in the MITRE ATT&CK framework, particularly concerning privilege escalation and initial access. Attackers could exploit such vulnerabilities to establish persistence within a network, ultimately facilitating more extensive assaults on targeted organizations.
As cyber threats evolutionarily advance, business owners must maintain vigilance and enhance their security protocols to safeguard against similar vulnerabilities. Ensuring robust oversight of IAM roles and staying informed about security updates can significantly mitigate the risks posed by such exploits.