CVE-2026-18255 in Quay
Summary
by MITRE • 07/29/2026
A flaw was found in Quay. A user configured in GLOBAL_READONLY_SUPER_USERS is able to view robot account tokens for repositories they are not a member of, allowing an attacker with read-only superuser privileges to impersonate any robot account.
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Analysis
by VulDB Data Team • 07/29/2026
This vulnerability exists within the Quay container registry platform where improper access control mechanisms allow certain privileged users to bypass repository membership restrictions. The flaw specifically affects the GLOBAL_READONLY_SUPER_USERS configuration setting which grants read-only access but inadvertently permits token enumeration across repositories outside of the user's assigned permissions. This represents a critical privilege escalation vulnerability that undermines the fundamental security model of repository-based access controls.
The technical implementation flaw stems from inadequate authorization checks during robot account token retrieval operations. When a user with GLOBAL_READONLY_SUPER_USERS privileges attempts to access robot account tokens, the system fails to properly validate whether the requesting user has legitimate access rights to the target repository. This occurs due to missing or insufficient repository membership verification logic that should normally enforce access boundaries between different repository namespaces. The vulnerability manifests as an information disclosure issue where sensitive authentication tokens can be accessed without proper authorization, enabling unauthorized impersonation of robot accounts across repository boundaries.
The operational impact of this vulnerability is severe and multifaceted within container registry environments. An attacker with read-only superuser privileges could leverage this flaw to access robot account tokens for repositories they do not belong to, potentially gaining persistent access to critical container images and build processes. This capability enables unauthorized users to perform actions such as pushing new images, pulling restricted content, or manipulating repository configurations without detection. The vulnerability essentially allows for privilege escalation from read-only access to full administrative capabilities across multiple repositories, creating a significant risk for organizations relying on Quay for container image management.
This vulnerability aligns with CWE-285 (Improper Authorization) and represents a failure in the principle of least privilege enforcement within the application's security architecture. The flaw also relates to ATT&CK technique T1078.004 (Valid Accounts: Cloud Accounts) as it allows unauthorized access to legitimate robot accounts through compromised superuser privileges. Organizations should implement immediate mitigations including reviewing and restricting GLOBAL_READONLY_SUPER_USERS configurations, implementing stricter repository access controls, and monitoring for unauthorized token access patterns. Additionally, regular security audits of access control mechanisms and mandatory code reviews for authorization logic should be enforced to prevent similar issues in other components of the system.
The root cause analysis reveals that this vulnerability likely stems from insufficient input validation and access control implementation during token retrieval operations. The system fails to properly enforce repository-level boundaries even when users possess elevated privileges, creating an access control bypass scenario. This type of flaw commonly occurs in applications where administrative privileges are granted without proper consideration for repository-specific access controls, particularly in multi-tenant environments where isolation between different user groups is critical.
Organizations should prioritize immediate patching and configuration review to address this vulnerability while implementing additional monitoring controls around robot account token access patterns. The security team should establish alerts for unusual token retrieval activities and conduct comprehensive access control assessments across all Quay configurations. This vulnerability underscores the importance of maintaining strict separation between administrative privileges and repository-specific access rights, particularly in systems handling sensitive container image repositories and automated deployment workflows.