CVE-2026-117468 in Psono
Summary
by MITRE • 10/27/2026
Psono Server versions 5.3.5 through 7.2.3 used a permission class that did not enforce token write scope when claiming a device code. An authenticated remote attacker holding a restricted API key-derived session could claim an attacker-controlled device code and obtain a full read-write session valid for up to 365 days, bypassing the original token's scope and lifetime restrictions. This did not bypass two-factor authentication or directly disclose plaintext secrets.
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Analysis
by VulDB Data Team • 10/27/2026
The vulnerability identified in Psono Server versions ranging from 5.3.5 through 7.2.3 represents a critical flaw in the application’s access control logic, specifically within the mechanism used for claiming device codes during an OAuth-like authorization flow. The core technical issue stems from a misconfigured permission class that fails to validate or enforce the write scope restrictions associated with the API key-derived session token held by the authenticated user. In standard secure implementations, when a client requests to claim a device code, the server must verify that the requesting session possesses sufficient privileges for the specific action being performed. However, in this instance, the system incorrectly assumes that any valid authentication is sufficient for claiming the device code, regardless of whether the original token was restricted to read-only operations or limited scopes. This oversight allows an attacker who has obtained a restricted API key and established a corresponding session to interact with the endpoint responsible for device code claims without triggering appropriate authorization failures.
From an operational perspective, this flaw enables privilege escalation that significantly compromises the integrity of the authentication system. An authenticated remote attacker can leverage their existing, albeit limited, credentials to claim an attacker-controlled device code. Upon successful claiming, the server issues a new session token that is not bound by the original restrictions. This newly minted token grants full read-write access and remains valid for up to 365 days, effectively bypassing both the scope limitations and the intended lifetime constraints of the initial credential set. The impact is severe because it allows an attacker with minimal privileges to escalate their rights to administrative levels without needing to crack passwords or exploit additional vulnerabilities in the authentication backend. This prolonged validity period exacerbates the risk by providing a persistent foothold within the system, allowing for sustained unauthorized access and potential data exfiltration over an extended timeframe.
It is important to note that while this vulnerability facilitates significant privilege escalation, it does not directly compromise two-factor authentication mechanisms nor does it result in the immediate disclosure of plaintext secrets such as passwords or encryption keys stored by Psono. The attack vector relies entirely on the misuse of valid session tokens and the flawed enforcement of API scopes rather than breaking cryptographic protections or bypassing multi-factor challenges. Consequently, defenders must recognize that even restricted accounts can serve as a launchpad for broader system compromise if scope validation is not rigorously enforced at every step of the authorization process. This scenario highlights the importance of implementing strict principle-of-least-privilege checks during token exchange and device claim operations to prevent lateral movement within authenticated environments.
To mitigate this vulnerability, organizations running Psono Server must immediately upgrade to a version later than 7.2.3 where the permission class has been corrected to properly enforce write scope requirements when claiming device codes. In addition to upgrading, administrators should audit existing API keys and sessions to identify any potentially compromised tokens resulting from exploitation of this flaw before the patch is applied. Implementing stricter token validation policies that verify both read and write scopes during all state-changing operations can further harden the system against similar logic flaws. This issue aligns with CWE-269, which describes Improper Privilege Management, as it involves a failure to enforce proper access control levels for an actor. Furthermore, from a threat modeling perspective using MITRE ATT&CK techniques, this vulnerability facilitates Account Manipulation and potentially Credential Access through the abuse of valid credentials to gain higher-level permissions, underscoring the need for robust identity governance and continuous monitoring of privilege escalation events within the application layer.