CVE-2022-39387 is a security vulnerability classified under CWE-287 (Improper Authentication) affecting the xwiki-contrib OIDC (OpenID Connect) module prior to version 1.29.1. XWiki is a popular open-source wiki platform used for collaborative content management, and the OIDC module integrates OpenID Connect authentication to allow users to log in via external identity providers. The vulnerability arises because the module improperly handles the configuration of OpenID providers. Even if an administrator has configured a specific OpenID provider in the xwiki.properties file, an attacker can override this configuration by supplying arbitrary OpenID provider details through HTTP request parameters (specifically via oidc.endpoint.* parameters). This flaw allows an attacker to bypass the intended authentication mechanism entirely by specifying their own OpenID provider or even an XWiki-based OpenID provider using the oidc.xwikiprovider parameter. Furthermore, the attacker can manipulate group mappings via the oidc.groups.mapping parameter to automatically assign themselves to privileged groups such as the XWikiAdminGroup. This effectively grants administrative privileges without proper authentication. The vulnerability requires no prior authentication or user interaction, making it exploitable remotely by anyone able to send crafted requests to the vulnerable XWiki instance. The issue has been patched in version 1.29.1 of the OIDC module, and no workaround exists other than upgrading to the fixed version. No known exploits have been reported in the wild as of the published date (November 2022).

The impact of CVE-2022-39387 on European organizations using vulnerable versions of the XWiki OIDC module is significant. Successful exploitation allows an attacker to bypass authentication controls and gain unauthorized administrative access to the wiki platform. This can lead to full compromise of the wiki content, including the ability to modify, delete, or exfiltrate sensitive information stored within the wiki. Given that wikis are often used for internal documentation, project collaboration, and knowledge sharing, unauthorized access can result in intellectual property theft, disruption of business processes, and potential exposure of confidential data. Additionally, attackers with admin privileges could create backdoors, add malicious content, or pivot to other internal systems if the wiki is integrated with broader enterprise infrastructure. The lack of required authentication or user interaction increases the risk of automated or opportunistic attacks. Although no known exploits are reported, the medium severity rating reflects the potential for serious confidentiality, integrity, and availability impacts if exploited. For European organizations, especially those in regulated sectors such as finance, healthcare, or government, such a breach could also lead to compliance violations under GDPR and other data protection regulations.

The only effective mitigation for CVE-2022-39387 is to upgrade the xwiki-contrib OIDC module to version 1.29.1 or later, where the vulnerability has been patched. Organizations should prioritize this upgrade in their patch management cycles. Beyond upgrading, organizations should implement the following specific measures: 1) Restrict access to the XWiki instance to trusted networks or VPNs to reduce exposure to unauthenticated external requests. 2) Implement web application firewalls (WAFs) with custom rules to detect and block suspicious requests containing oidc.endpoint.* or oidc.groups.mapping parameters that are not expected in normal operation. 3) Conduct thorough audits of user and group memberships in XWiki to detect any unauthorized administrative accounts created via exploitation. 4) Monitor logs for anomalous authentication attempts or parameter tampering indicative of exploitation attempts. 5) If possible, disable or limit the use of dynamic OpenID provider configuration via request parameters, enforcing static configuration only. 6) Educate administrators and developers about secure configuration practices for authentication modules. These targeted mitigations complement the mandatory upgrade and help reduce risk during the transition period.