CVE-2026-55671 in ZITADEL
Summary
by MITRE • 07/10/2026
ZITADEL is an open source identity management platform. From 4.0.0-rc.1 through 4.15.1, ZITADEL's HTTP notification channels, OIDC BackChannel Logout, and SAML metadata URL fetches do not consistently validate user-defined URLs against protected denylist handling, allowing server-side requests to loopback, internal IP, link-local, or redirected endpoints through DNS rebinding, redirects, or protocol downgrades. This issue is fixed in version 4.15.2.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 07/10/2026
ZITADEL represents a comprehensive open source identity management platform that serves as a critical component in modern authentication infrastructures. The vulnerability identified affects versions ranging from 4.0.0-rc.1 through 4.15.1, specifically targeting the platform's HTTP notification channels, OIDC BackChannel Logout functionality, and SAML metadata URL fetch mechanisms. These components are fundamental to ZITADEL's ability to communicate with external systems and maintain secure authentication flows. The flaw manifests in the inconsistent validation of user-defined URLs against protected denylist handling, creating a significant security gap that could be exploited by malicious actors to bypass intended network restrictions.
The technical implementation of this vulnerability stems from inadequate input validation within ZITADEL's URL processing mechanisms. When users configure notification endpoints, OIDC logout URLs, or SAML metadata locations, the system fails to consistently enforce denylist restrictions that should prevent access to internal network resources. This weakness enables attackers to craft malicious URLs that leverage DNS rebinding techniques, HTTP redirects, or protocol downgrades to access loopback addresses, internal IP ranges, and link-local endpoints that should remain protected from external access. The vulnerability essentially allows an attacker to perform server-side request forgery attacks where the target system makes requests to internal resources that would normally be inaccessible from external networks.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates potential entry points for lateral movement within network environments. Attackers could exploit this flaw to access internal services, databases, or administrative interfaces that are typically shielded by network segmentation and firewall rules. The implications are particularly severe in enterprise environments where ZITADEL might be integrated with critical infrastructure components, as successful exploitation could enable unauthorized access to sensitive systems and data. This vulnerability directly aligns with CWE-918, Server-Side Request Forgery, which specifically addresses the issue of unvalidated user input being used to make server-side requests to internal resources.
The threat landscape surrounding this vulnerability is further exacerbated by the fact that it affects core authentication mechanisms that are essential for identity management operations. When attackers can bypass network restrictions through DNS rebinding or redirect attacks, they gain access to privileged information and potentially escalate their privileges within the authenticated environment. This flaw creates an attack surface that could be leveraged for reconnaissance activities, credential harvesting, or more sophisticated attacks targeting internal services. The vulnerability's impact is amplified by its presence in multiple critical components of ZITADEL's architecture, increasing the likelihood of successful exploitation across different scenarios within the platform's operational environment.
Organizations deploying ZITADEL within their identity infrastructure should prioritize immediate mitigation through upgrading to version 4.15.2, which contains the necessary fixes for this vulnerability. Additional defensive measures include implementing network-level restrictions on outbound HTTP requests from ZITADEL servers, monitoring for suspicious URL patterns in configuration settings, and establishing strict access controls around internal network resources that might be accessible through compromised authentication systems. The fix implemented in version 4.15.2 addresses the root cause by ensuring consistent validation of user-defined URLs against comprehensive denylists, including proper handling of DNS rebinding scenarios and redirect chains that could potentially bypass existing restrictions. This vulnerability serves as a reminder of the critical importance of input validation and network segmentation in identity management systems, particularly when dealing with external connectivity requirements and internal resource access patterns.