CVE-2026-55459 in goobi-viewer-core
Summary
by MITRE • 10/23/2026
The Goobi viewer is a web application that allows digitised material to be displayed in a web browser. From version 25.01 to before version 26.05, AuthenticationEndpoint.verifyOpenIdToken builds its verifier as JWT.require(algorithm).withIssuer(issuer).build() and does not enforce the aud claim during cryptographic validation. The aud check is performed manually afterwards via a single string-equality call, which only handles single-string aud values. In a multi-RP IdP setup, a token whose single-string aud matches the viewer's client ID but was issued for a different relying party passes the check and authenticates the attacker as the token's sub. This issue has been patched in version 26.05.
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Analysis
by VulDB Data Team • 10/23/2026
The Goobi Viewer is a widely used web application designed to display digitized cultural heritage materials, such as books, manuscripts, and images, within a standard web browser. A critical authentication flaw was identified in versions ranging from 25.01 up to, but not including, version 26.05. This vulnerability stems from an improper implementation of the OpenID Connect protocol's audience validation mechanism during the verification of JSON Web Tokens. Specifically, the AuthenticationEndpoint.verifyOpenIdToken method constructs a JWT verifier using the library call jwt.require(algorithm).withIssuer(issuer).build(). While this configuration correctly validates the cryptographic signature and checks that the token was issued by an expected issuer, it fails to enforce the aud claim at the cryptographic validation stage. Instead, the application relies on a manual post-validation check for the audience claim.
The technical flaw lies in how this manual verification is executed. The code performs a single string-equality comparison against the viewer's client ID rather than utilizing the robust list-based handling provided by standard JWT libraries or enforcing strict multi-audience support as defined in RFC 7800. In modern OpenID Connect deployments, particularly those involving multiple relying parties sharing an identity provider, it is common for a single access token to contain an aud claim that is either a JSON array of strings or contains values relevant to several services. The flawed implementation only handles cases where the aud claim is a simple string and matches exactly one specific client ID. Consequently, if an attacker obtains a valid JWT issued by a trusted identity provider but intended for a different relying party within the same ecosystem, they can exploit this logic error. Because the cryptographic signature remains valid and the issuer check passes, the application accepts the token as authentic for its own context simply because the single-string aud value happens to match the Goobi Viewer's client ID string, even though it was not intended for that specific service.
This vulnerability has severe operational implications in multi-relying party environments where a shared identity provider issues tokens with audience claims that might overlap or be misinterpreted due to loose validation logic. An attacker who can obtain such a token from another relying party could authenticate as any user identified by the sub claim within that token against the Goobi Viewer instance. This effectively bypasses authentication controls, allowing unauthorized access to digitized materials and potentially sensitive metadata associated with those items. In scenarios where the identity provider issues tokens for multiple services simultaneously or reuses audience values across different applications, this flaw could lead to widespread account takeover if an attacker can manipulate or intercept tokens intended for other systems within the same trust domain.
The issue has been addressed in version 26.05 of the Goobi Viewer by correcting the JWT verification logic to properly enforce the aud claim according to industry standards. To mitigate risks associated with this vulnerability, organizations running affected versions should immediately upgrade to version 26.05 or later. For environments where upgrading is not immediately feasible, administrators should ensure that identity providers do not issue tokens containing audience values that match Goobi Viewer's client ID unless those tokens are explicitly intended for the viewer. Additionally, implementing strict token binding and monitoring authentication logs for anomalous login patterns from unexpected relying parties can help detect potential exploitation attempts. This vulnerability aligns with CWE-287 Improper Authentication, as it involves a failure to correctly verify identity credentials due to flawed validation logic. It also relates to ATT&CK technique T1078 Valid Accounts, where attackers leverage legitimate but misused account tokens to gain unauthorized access to systems and data.