GraphQL Vulnerabilities (CSRF)
- Shone Pious
- Jul 3, 2024
- 4 min read
Updated: Jul 13, 2024
In this blog:
➡️ Find my blog on exposing private GraphQL endpoints here.
➡️ Find my blog on exposing private GraphQL fields here.
➡️ Find my blog on GraphQL vulnerabilities here.
How GraphQL works
GraphQL, created by Meta, is a flexible query language for APIs that improves client-server communication. It lets clients request exact data, minimizing large responses and reducing multiple calls common in REST APIs. With its type system, it allows front-end users to explore and request specific data, consolidating multiple requests into a single query. Users can also use arguments to fetch specific data from objects.
However, direct use of these arguments to fetch objects may expose the API to access control vulnerabilities like insecure direct object reference (IDOR). Furthermore, introspection, a feature enabling clients to query the server for schema information, poses risks of information disclosure, potentially allowing users to access sensitive data such as field descriptions.
GraphQL Vulnerabilities (CSRF)
Most GraphQL vulnerabilities arise from design and implementation flaws. Despite its efficiency, GraphQL's flexibility can introduce security gaps. A common vulnerability is Cross-Site Request Forgery (CSRF), which targets GraphQL APIs that accept vulnerable request types, such as GET requests or those with 'x-www-form-urlencoded' content type, unlike traditional CSRF attacks exploiting same-origin policy vulnerabilities.
Cross-Site Request Forgery (CSRF) is a web security vulnerability where attackers manipulate authenticated users into performing unintended actions on a target web application. This happens because browsers automatically include session cookies in requests, enabling attackers to execute actions from the user's account. Traditional CSRF exploits the same-origin policy, which restricts interactions to the same origin. Attackers often use hidden form submissions or AJAX requests to carry out malicious activities like changing passwords or deleting accounts.
A notable vulnerability involves GET-based CSRF attacks, facilitated by misconfigurations or the exposure of GraphiQL consoles intended for developer environments. These consoles can unwittingly allow unauthorized query or mutation requests, potentially leading to security breaches.
Steps in a GraphQL CSRF attack
1. Identify the target GraphQL API endpoint.
2. Find a mutation operation like changing the email.
3. Copy the mutation and modify it so that it is all in one line.
4. Once you have scripted a mutation query in HTML with the values encoded as HTML (using Burpsuite), put it into the form field like this:
➡️ You can see a CSRF demonstration with this payload here.
Potential CSRF impacts
APIs vulnerable to CSRF attacks can have severe consequences, such as unauthorized changes to account settings, password alterations, fund transfers, and data theft, particularly if sensitive information is stored on the website.
An illustrative case is the csurf incident in September 2022, where penetration testers discovered a critical CSRF vulnerability in the csurf open-source software during routine bug hunting. Following a customer's report of a missing secure flag in a CSRF cookie, Fortbridge, a UK cybersecurity firm, investigated. They found that the vulnerability was rooted in a node.js application relying on outdated csurf middleware. Despite its widespread use, csurf hadn't been updated for three years, leading to several vulnerabilities including insecure storage of secrets, usage of the vulnerable SHA-1 algorithm, lack of default cookie signature checks, inconsistent token validation, and allowance for empty XSRF tokens, enabling attackers to generate their own CSRF tokens.
The impacts of these vulnerabilities being exploited in the wild can be huge with financial loss being the best-case scenario for a lot of businesses. Other impacts include:
Data breaches: Attackers could gain unauthorized access to sensitive data stored within the GraphQL system, such as user accounts, personal information, or proprietary business data, leading to data breaches and compromising user privacy.
Reputation damage: Public disclosure of CSRF vulnerabilities can damage the reputation of the affected organization and erode user trust.
Legal consequences: Organizations may face legal liabilities, regulatory fines, or lawsuits due to CSRF attacks and associated data breaches.
Preventing an attack
To identify and exploit CSRF vulnerabilities, attackers must bypass defences on the target website and the victim's browser. A common defence is the use of CSRF tokens —unique, secret values generated by the server and stored in the user's session. When a client performs a sensitive action, the server verifies that the client's token matches the stored one. Tokens are usually sent to the client in a hidden form field via a POST request. However, a major flaw occurs when applications use a global pool of tokens rather than tying them to specific users, allowing attackers to inject a valid token from their own account into the victim's session.
Another method to prevent CSRF attacks is to set SameSite restrictions for cookies. Browsers like Chrome now default cookies to "SameSite=Lax" which limits cross-site requests that include specific cookies. Developers can manually set the SameSite attribute on cookies to control the contexts in which they are used, enhancing security against CSRF attacks.
The setting below lets users opt into cookie blocking:
POST requests that use a content type of application/json are known to be secure against CSRF, if the content type is properly validated by the server. This is because modern browsers enforce same-origin policy for requests with the application/json content type.
Alternatively, methods like GET requests or those with a content type of x-www-form-urlencoded are susceptible to CSRF attacks. These requests can be initiated by a browser without the user's explicit consent, posing a risk if the GraphQL endpoint accepts them.
Other more administrative approaches include:
Security audits and testing: Regularly conduct security audits and penetration testing of the GraphQL system to identify and address potential CSRF vulnerabilities and other security issues.
Multi-factor authentication (MFA): Require users to authenticate using multiple factors (e.g., password plus SMS code or biometric authentication) to mitigate the risk of unauthorized access and CSRF attacks.
Educate users: Raise awareness about the risks of clicking on suspicious links or executing unintended actions on web applications.
Thank you for reading!
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