CVE-2026-78231 in Gitea
Summary
by MITRE • 10/15/2026
When OpenID sign-in is enabled, Gitea processes unauthenticated assertion parameters and sends an HTTP POST request to the caller-supplied OpenID provider endpoint during verification. An attacker controls the destination and much of the form body, allowing interaction with internal HTTP services reachable from the Gitea server. The response is not returned to the attacker, so the issue is blind SSRF; its impact depends on the services and network addresses the server can reach.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified in Gitea represents a critical Server-Side Request Forgery (SSRF) flaw that emerges specifically when OpenID Connect authentication is enabled within the application environment. This security defect stems from an insufficient validation of user-supplied input during the assertion verification phase of the OpenID sign-in process. When a user initiates login, Gitea constructs and sends an HTTP POST request to the endpoint provided by the caller as part of the OpenID configuration or authentication flow. The core technical flaw lies in the application's failure to strictly validate the destination URL against a predefined allowlist or internal network boundaries before dispatching this request. Consequently, an attacker who can influence the parameters passed during the sign-in process gains significant control over both the target host and port of the outgoing HTTP POST request, as well as substantial portions of the form body data included in that request.
This lack of rigorous input validation transforms a standard authentication mechanism into a vector for blind SSRF attacks. Because Gitea acts as an intermediary proxy to external services based on attacker-controlled inputs, it can be manipulated to interact with internal HTTP services that are not intended to be publicly accessible or even reachable from the general internet but may be exposed within the local network segment where the Gitea server resides. The impact of this vulnerability is heavily dependent on the specific network architecture and the types of internal services running behind firewalls or security groups adjacent to the Gitea deployment. By directing requests toward these internal endpoints, an attacker can probe for sensitive information, trigger unintended actions within backend systems such as cloud metadata services, database interfaces, or administrative panels that lack proper authentication mechanisms when accessed from trusted local networks.
The classification of this issue as a blind SSRF is significant because the HTTP response generated by the targeted internal service is not returned to the attacker's browser or client application. This characteristic complicates exploitation for data exfiltration through direct response parsing, yet it does not diminish the severity of the threat. The primary risk lies in the ability to trigger side effects on vulnerable internal services, such as causing denial-of-service conditions by sending high-volume requests, exploiting server-side request forgery chains that lead to remote code execution via other vulnerabilities in backend systems, or performing port scanning and network reconnaissance against internal infrastructure. Attackers can leverage this blind channel to map out the internal network topology and identify further attack surfaces within the organization's private environment.
From a standards perspective, this vulnerability aligns with CWE-918, which describes Server-Side Request Forgery (SSRF) flaws where the server makes requests based on user input without proper validation of the destination. It also maps to MITRE ATT&CK technique T1571, specifically Non-Standard Port or Protocol usage if attackers exploit less common ports, and generally falls under the broader category of SSRF as a method for lateral movement within compromised networks. The exploitation path typically involves manipulating the OpenID provider URL field during login attempts to point toward internal IP addresses or localhost endpoints, thereby bypassing traditional perimeter defenses that only monitor external traffic patterns.
To mitigate this vulnerability, immediate remediation should focus on implementing strict allowlisting mechanisms for all outgoing HTTP requests initiated by Gitea. Administrators must ensure that the application is configured to reject any destination URLs that do not match a predefined list of trusted OpenID provider domains and IP ranges. Additionally, network-level controls such as firewall rules or security groups should be enforced to restrict outbound traffic from the Gitea server container or host to only those ports and protocols necessary for legitimate external communication. Disabling public access to internal services is also critical; even if SSRF is mitigated at the application level, ensuring that backend services require authentication regardless of source IP provides a vital defense-in-depth layer. Regular security audits and static code analysis focused on input validation in authentication flows can help prevent similar issues from being introduced during future development cycles.