MineforgianSSRF Bypass Via DNS Rebinding Found in datamodel-code-generator
Security vulnerability allows attackers to bypass network restrictions and access internal services through a Time-of-Check to Time-of-Use flaw.
A significant security vulnerability has been identified in datamodel-code-generator, a Python tool often used in development workflows for generating data models. The flaw, detailed in a GitHub Security Advisory, allows for a Server-Side Request Forgery (SSRF) protection bypass through a technique known as DNS rebinding. This critical issue could enable attackers to circumvent intended network restrictions and gain unauthorized access to internal services, even when safeguards against private network access are enabled.
Understanding the Vulnerability
The datamodel-code-generator tool, designed to generate data models from various schema definitions, includes an anti-SSRF guard to prevent it from connecting to private or internal network addresses. This guard relies on validating the resolved IP address of a target URL. However, the advisory highlights a critical Time-of-Check to Time-of-Use (TOCTOU) vulnerability in how this validation is implemented.
Specifically, the tool performs two distinct DNS resolutions: one for initial validation and another for the actual HTTP connection. The vulnerability arises because the validated IP address is not "pinned" or carried over to the connection phase.
How it Works: The DNS Rebinding Attack
The attack vector leverages DNS rebinding, a technique where an attacker manipulates DNS records to change the IP address associated with a hostname between two distinct network operations.
- Validation Phase: When
datamodel-code-generatorinitiates a fetch, its_validate_url_for_fetch()function resolves the target hostname using_get_ips_from_host()(viasocket.getaddrinfo). An attacker can configure a low-TTL (Time-To-Live) DNS record to resolve to a public, "safe" IP address during this initial check. This allows the URL to pass the anti-SSRF guard, which is designed to block non-global or private addresses. - Connection Phase: Immediately after validation, the tool proceeds to establish an HTTP connection using
httpx.get(). Crucially,httpxperforms its own independent DNS resolution for the connection. In the brief time window between validation and connection, the attacker-controlled DNS record can be updated to resolve the same hostname to a private IP address (e.g.,127.0.0.1for loopback,169.254.169.254for link-local cloud-metadata endpoints, or other internal network services).
Because the connection is not tied to the IP address that passed the initial validation, the httpx client will then connect to the private IP, effectively bypassing the allow_private_network=False safeguard. The advisory notes that while the redirect-handling loop does correctly re-validate each redirect URL, the initial validation-to-connection flow remains susceptible.
Impact and Reachability
This Server-Side Request Forgery vulnerability is reachable when datamodel-code-generator is used to fetch an attacker-influenced URL. This includes scenarios where the tool processes remote $ref references within schema definitions or when a malicious URL is supplied via its --url command-line argument.
The successful exploitation of this flaw could allow attackers to:
- Access internal network services or APIs that are not publicly exposed.
- Retrieve sensitive data from internal systems.
- Perform actions on internal services, potentially leading to further compromise.
Why this Matters
For developers, server administrators, and anyone utilizing datamodel-code-generator within their Minecraft-related projects or general development pipelines, this vulnerability presents a significant risk. While not directly affecting Minecraft servers themselves, any backend services or tools that integrate with datamodel-code-generator for tasks like API documentation generation or data model synchronization could be exposed.
- Developers: If your applications or build processes use
datamodel-code-generatorto process external or untrusted schema definitions, you must ensure that input URLs are rigorously sanitized or that network access for the tool is appropriately restricted. - Server Administrators: It's crucial to review the security posture of all tools processing external input, especially those with network access. Consult our /tech section for more security advisories.
- Tool Users: Be cautious when using
datamodel-code-generatorwith untrusted URLs or schema files that contain remote references, as this could inadvertently expose your internal network.
Addressing this vulnerability typically involves ensuring that DNS resolution results are consistently applied throughout the connection process, or by implementing more robust network access controls. Users should monitor for official patches and updates to datamodel-code-generator to mitigate this risk.
Timeline
| Date | Event |
|---|---|
| 2026-07-28 | GitHub Security Advisory published detailing SSRF vulnerability in datamodel-code-generator. |
FAQ
What is `datamodel-code-generator`?
It's a Python tool that generates data models from various schemas, such as OpenAPI or JSON Schema, often used in development workflows.
What is SSRF?
SSRF, or Server-Side Request Forgery, is a vulnerability that allows an attacker to induce the server-side application to make HTTP requests to an arbitrary domain chosen by the attacker, potentially accessing internal resources.
How does DNS rebinding work in this context?
An attacker-controlled DNS record changes its resolution between the initial security check (resolving to a public IP) and the actual connection (resolving to a private IP), thereby tricking the server into connecting to an internal resource.
Who is affected by this vulnerability?
Users and developers of applications that utilize datamodel-code-generator to fetch attacker-influenced URLs are affected, particularly where allow_private_network=False is intended to prevent access to internal services.