CVE-2026-116870 in Octopus Server
Summary
by MITRE • 10/27/2026
In affected versions of Octopus Server, OIDC token issuer validation was performed inconsistently. This could result in a token issued from a suitably configured non legitimate issuer being accepted as a token belonging to a service account from a legitimate trusted issuer. Exploitation requires a service account with at least one OIDC identity configured. An attacker would also need to know or guess some details of that identity in order to be in a position to attempt exploitation.
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Analysis
by VulDB Data Team • 10/27/2026
The vulnerability identified in Octopus Server represents a critical flaw in the implementation of OpenID Connect authentication protocols, specifically concerning the validation of token issuers. In secure OAuth 2.0 and OIDC implementations, strict verification of the issuer claim within JSON Web Tokens is essential to ensure that tokens originate from trusted identity providers. The affected versions exhibited inconsistent behavior during this validation process, failing to rigorously enforce trust boundaries for all authentication paths or service account configurations. This inconsistency creates a scenario where an attacker can bypass standard security controls by presenting a token issued by a maliciously configured entity rather than the expected legitimate issuer.
From a technical perspective, the core issue lies in how the server processes and validates the iss claim within incoming OIDC tokens. When a user or service account attempts to authenticate using OpenID Connect, the server must verify that the token was signed by an authority it trusts. The flaw allows for the acceptance of tokens from non-legitimate issuers if specific conditions are met during the validation routine. This bypasses the intended authentication mechanism, effectively allowing unauthorized access under the guise of a valid service account identity. Such behavior deviates significantly from established security best practices and introduces severe risks to system integrity.
The operational impact of this vulnerability is substantial for organizations relying on Octopus Server for deployment automation and infrastructure management. If exploited successfully, an attacker could gain elevated privileges by impersonating legitimate service accounts. This access can lead to unauthorized deployments, data exfiltration, or further lateral movement within the network environment. The severity is compounded by the fact that these servers often hold administrative credentials necessary to manage critical production systems, making them high-value targets for adversaries seeking persistent access or disruptive capabilities.
Exploitation of this vulnerability requires specific prerequisites and conditions. First, there must be at least one service account configured with an OIDC identity within the Octopus Server environment. Second, the attacker needs knowledge or ability to guess certain details regarding that specific identity configuration. This requirement suggests that while the flaw is severe, it may not be trivially exploitable in all environments without prior reconnaissance or insider information about the authentication setup. However, given the potential for automated attacks and credential stuffing techniques, this barrier should not be underestimated as a reliable defense mechanism.
To mitigate these risks, immediate action is required to update Octopus Server to versions where the OIDC token issuer validation logic has been corrected. Administrators should ensure that all instances are patched against this inconsistency. Additionally, organizations should review their service account configurations and consider implementing additional layers of security such as multi-factor authentication for administrative access or restricting network exposure of management interfaces. Regular audits of identity provider trust relationships can also help detect any misconfigurations before they lead to compromise.
This vulnerability aligns with CWE-287, which describes Improper Authentication, specifically regarding the failure to properly verify credentials from external sources. It also relates to CWE-345, Insufficient Verification of Data Authenticity, as the system failed to adequately validate the origin and integrity of the authentication tokens presented by users or services. Understanding these classifications helps in applying standardized remediation strategies and improving overall security posture against similar attacks.
Furthermore, this incident reflects tactics observed in ATT&CK framework techniques related to Initial Access via Valid Accounts and potentially Account Manipulation if an attacker were able to alter existing service account configurations. The ability to accept tokens from untrusted issuers facilitates unauthorized entry points that can be leveraged for subsequent phases of attack such as privilege escalation or persistence establishment. Security teams should monitor logs for anomalous authentication patterns involving OIDC providers not previously seen in normal operations to detect potential exploitation attempts early.
In summary, the inconsistent validation of OIDC token issuers in Octopus Server poses a significant threat to organizational security by allowing unauthorized access through forged tokens. The combination of technical flaws and specific environmental prerequisites makes this vulnerability both potent and targeted. Prompt patching is essential, alongside broader reviews of authentication configurations and monitoring strategies to ensure robust protection against identity-based attacks. Maintaining strict adherence to OIDC standards and regularly updating software components are vital steps in preventing such vulnerabilities from being exploited in production environments.