CVE-2026-101029 in Gitea
Summary
by MITRE • 10/06/2026
Gitea's repository migration and pull mirror egress checks could be bypassed with a hostname that returns multiple DNS answers, because the address that was validated was not necessarily the address Git later connected to. A low-privileged user who can create migrations or mirrors could direct the server to internal services, reading from and writing to reachable internal Git or HTTP endpoints. Content from internal responses could additionally be disclosed through migration and mirror error messages.
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Analysis
by VulDB Data Team • 10/07/2026
The vulnerability in Gitea represents a critical flaw within its repository migration and pull mirroring subsystems, specifically concerning the validation of destination hostnames during egress traffic generation. This issue stems from a fundamental mismatch between the domain name resolution process used for security checks and the actual network connection established by the underlying Git client library. When an administrator or user initiates a migration or mirror operation pointing to a remote repository, Gitea performs a DNS lookup on the provided hostname to verify that it does not resolve to internal, private IP addresses such as those defined in RFC 1918. The system relies on this initial validation step to prevent Server-Side Request Forgery (SSRF) attacks against internal infrastructure. However, the implementation fails to ensure consistency between the address validated during this check and the specific IP address selected for the actual Git connection.
The core technical flaw arises from how DNS resolution handles multiple records. If a hostname is configured in DNS to return multiple A or AAAA records, including both public internet addresses and private internal network addresses, Gitea may validate against one of these addresses while allowing Git to connect via another. For instance, if the validation logic selects an external IP address for its safety check, but the operating system's resolver subsequently chooses a private internal IP from the same set of records for the actual TCP connection, the security boundary is effectively bypassed. This behavior allows attackers who have low-privileged access capable of creating migrations or mirrors to trick the Gitea server into connecting to internal services that should be inaccessible from the public-facing application layer.
The operational impact of this vulnerability is severe, as it enables unauthorized lateral movement within an organization's network architecture. An attacker can exploit this flaw to direct the Gitea server to read data from or write data to reachable internal Git repositories, HTTP endpoints, database interfaces, or other sensitive services running on private networks. This capability effectively transforms a code hosting platform into a pivot point for attacking internal infrastructure. Furthermore, the vulnerability facilitates information disclosure through error handling mechanisms. When the connection attempt fails due to authentication issues, network restrictions, or protocol mismatches at the target internal service, Gitea may expose details from the server's response in its own migration or mirror failure messages. This side channel can reveal sensitive technical details about the internal services, such as software versions, configuration structures, or error traces, aiding further exploitation attempts against other systems within the network perimeter.
This vulnerability aligns with CWE-918, which describes Server-Side Request Forgery (SSRF) flaws where a web application fetches a remote resource without validating the user-provided URL properly. It also maps to MITRE ATT&CK technique T1557, specifically Adversary-in-the-Middle or Lateral Tool Transfer scenarios where an attacker uses compromised systems to access other resources on the local network. The failure lies in CWE-20, Improper Input Validation, as the application does not adequately verify that all aspects of the input (in this case, every potential IP address returned by DNS) adhere to security policies before proceeding with sensitive operations.
To mitigate this risk, organizations running Gitea must apply the latest available patches provided by the development team, which enforce strict validation against all resolved IP addresses rather than just a single one. In environments where immediate patching is not feasible, network-level controls should be implemented to restrict outbound connections from the server hosting Gitea. This includes configuring firewalls or security groups to block direct access to private IP ranges unless explicitly required for legitimate business operations. Additionally, administrators should review and harden error messages returned by migration and mirror processes to ensure they do not leak internal service details to unauthenticated users. Regular audits of user permissions are also recommended to limit the ability of low-privileged accounts to initiate external repository connections, thereby reducing the attack surface available to potential adversaries seeking to exploit this DNS resolution bypass mechanism.