Recently, a new vulnerability has been discovered in the UriComponentsBuilder library (CVE-2024-22243), which may impact applications that perform validation checks on URLs. This vulnerability could potentially allow attackers to conduct an open redirect or a Server-Side Request Forgery (SSRF) attack after the URL passes the validation checks.

In this post, we will discuss the technical details of this vulnerability, show a code snippet demonstrating how it may be exploited, and provide links to original references for further reading.

Technical Details

Applications that handle URLs are often susceptible to abuse by crafting malicious URLs. Specifically, this vulnerability affects applications that:

Perform validation checks on the host of the parsed URL.

When an attacker can control the input URL and bypass the host validation checks, they can exploit this vulnerability for open redirect and SSRF attacks.

An open redirect vulnerability allows an attacker to redirect visitors of a legitimate site to a different, potentially malicious site by crafting a URL that passes the validation checks but redirects to the attacker-controlled site.

SSRF occurs when an attacker forces a server to make a request to an arbitrary URL, which can lead to unauthorized access to internal resources, denial-of-service attacks, or remote code execution.

Here's an example of a vulnerable code snippet that uses UriComponentsBuilder and host validation

import org.springframework.web.util.UriComponentsBuilder;

public class URLValidator {
    public boolean isValidURL(String inputURL) {
        UriComponentsBuilder uriComponents = UriComponentsBuilder.fromHttpUrl(inputURL);
        String host = uriComponents.build().getHost();

        // Perform host validation
        if (isTrustedHost(host)) {
            return true;
        } else {
            return false;
        }
    }

    private boolean isTrustedHost(String host) {
        // Check if the host is trusted
        // ...
    }
}

In the code above, we see that the isValidURL method parses the input URL using UriComponentsBuilder.fromHttpUrl(inputURL). Then, it extracts the host part and performs a validation check using isTrustedHost(host). If the host is trusted, the method returns true.

However, by carefully crafting a URL, an attacker could potentially bypass these checks. Depending on how the parsed URL is used later in the application, this might lead to an open redirect or SSRF attack.

Note that this is just an example of how the vulnerability might be exploited, and real-world exploitation might differ based on the specific implementation.

The official CVE entry for this vulnerability

1. CVE-2024-22243: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-22243

2. CWE-601: Open Redirect: https://cwe.mitre.org/data/definitions/601.html
3. Original report of the issue:

Mitigation

To mitigate this vulnerability, it's crucial to perform appropriate host validation checks and escape any external input that is used for constructing URLs. Additionally, consider using up-to-date libraries and applying security patches promptly.

Stay tuned for further updates on this vulnerability, and always ensure that you are using the most secure methods and algorithms in your applications.

Timeline

Published on: 02/23/2024 05:15:08 UTC
Last modified on: 02/23/2024 16:14:43 UTC