CVE-2026-113374 in Nexus Repository
Summary
by MITRE • 11/04/2026
Sonatype Nexus Repository 3 does not require realm administration permission when a user creates a Rut Auth capability. A user who holds only the capability creation permission (nexus:capabilities:create) can create this capability, which turns on header-based authentication for the instance. A remote client can then authenticate as an existing user, including an administrator, without credentials.
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Analysis
by VulDB Data Team • 11/04/2026
The vulnerability identified in Sonatype Nexus Repository 3 represents a critical authorization bypass that fundamentally undermines the security model of the application by allowing unprivileged users to escalate their privileges through misconfigured authentication mechanisms. Specifically, the flaw resides in the permission checks associated with creating repository capabilities within the Rut Auth subsystem. Under normal operational parameters, administrative actions such as modifying global authentication settings should require elevated permissions, typically involving realm administration rights or specific security configuration roles. However, due to an insufficient access control check, a user possessing only the basic capability creation privilege, denoted as nexus:capabilities:create, is able to instantiate a Rut Auth capability without any further verification of their administrative status. This discrepancy in permission enforcement allows standard users to alter core authentication configurations that are intended to be restricted exclusively to system administrators.
The technical consequence of this misconfiguration is severe, as it enables the activation of header-based authentication for the entire instance. Header-based authentication relies on HTTP headers provided by a client or an intermediary proxy to identify and authenticate users, rather than requiring traditional credentials such as passwords or API keys. Once this capability is created and activated by the unprivileged user, the Nexus Repository begins to trust these incoming headers blindly. This creates a direct pathway for remote attackers to impersonate any existing user account on the system. By crafting HTTP requests that include specific header values corresponding to high-privilege accounts, such as administrators or users with write access to repositories, an attacker can bypass all standard login mechanisms and gain immediate access under those identities without ever providing valid credentials.
The operational impact of this vulnerability is profound, affecting both data integrity and system availability. An authenticated administrator account typically possesses unrestricted read and write access to all repositories, including the ability to deploy artifacts, delete content, and modify repository configurations. If an attacker successfully exploits this flaw to impersonate such a user, they can inject malicious software into public or private repositories, leading to supply chain compromise for downstream consumers who rely on these artifacts. Furthermore, the attacker could exfiltrate sensitive proprietary code or configuration data stored within the repository. The ability to act as any user also facilitates lateral movement if the Nexus instance is integrated with other systems that trust its authentication assertions, potentially expanding the scope of the breach beyond the immediate application environment.
This vulnerability aligns closely with CWE-269, which describes Improper Privilege Assignment, specifically where a lower-privileged actor can perform actions reserved for higher-privileged roles due to flawed access control logic. In terms of offensive security frameworks, this exploit maps directly to MITRE ATT&CK technique T1078, Valid Accounts, as it involves the misuse of legitimate credentials or identities through impersonation rather than credential theft. It also relates to T1528, Steal Application Access Token, in contexts where header-based authentication is used for service-to-service communication that might be hijacked via this misconfiguration. The root cause lies not in a buffer overflow or injection flaw but in the logical design of the authorization subsystem failing to enforce role-based access control boundaries correctly during capability initialization.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. Administrators should immediately apply any available patches from Sonatype that correct the permission checks for Rut Auth capabilities, ensuring that only users with explicit realm administration or security configuration permissions can modify authentication settings. In environments where patching is not instantly feasible, network-level controls such as firewalls or reverse proxies should be configured to restrict access to the Nexus Repository management interface exclusively to trusted IP addresses and administrative networks. Additionally, organizations should audit their current user roles and capabilities to ensure that the nexus:capabilities:create permission is granted only to users who genuinely require it for repository maintenance, adhering to the principle of least privilege. Regular security audits focusing on authentication configuration changes can help detect such misconfigurations early before they are exploited by malicious actors seeking to compromise software supply chains or internal systems.