As technology advances at an unprecedented pace, software vulnerabilities are becoming more common and complex. One such vulnerability has been discovered in the Omnissa UAG (Universal Access Gateway) platform. In this long read post, we will be discussing the details of the CVE-2025-25234 vulnerability, which is related to a Cross-Origin Resource Sharing (CORS) bypass, allowing potential bad actors to exploit this security flaw to gain unauthorized access to sensitive networks. We will cover the technical explanation of the vulnerability, a sample code snippet, useful references and links, and detailed steps of the exploit process.

Technical Explanation

Cross-Origin Resource Sharing (CORS) is a security feature implemented in web applications to restrict the resources that can be accessed by another domain to enhance security. In the case of Omnissa UAG, it has been discovered that there is a security flaw that allows a malicious actor to bypass the administrator-configured CORS restrictions and gain unauthorized access to protected networks.

This type of vulnerability (CVE-2025-25234) is deemed critical, as it can potentially allow attackers to steal sensitive information, manipulate data, and execute other harmful actions within the compromised network.

Sample Code Snippet

The vulnerability can be exploited by an attacker using standard JavaScript functions that are available on modern web browsers. Below is a code snippet that illustrates the exploitation technique:

const xhr = new XMLHttpRequest();
xhr.open('GET', 'https://target-omnissa-uag/api/secure-data';, true);
xhr.withCredentials = true;
xhr.onreadystatechange = function () {
  if (xhr.readyState === 4 && xhr.status === 200) {
    const sensitiveData = JSON.parse(xhr.responseText);
    console.log('Sensitive data retrieved:', sensitiveData);
  }
};
xhr.send(null);

In this example, the attacker creates a JavaScript XMLHttpRequest object to send a request to the target Omnissa UAG, specifically fetching sensitive data. By setting the withCredentials property to true, the attacker can bypass the CORS restrictions, which should prevent unauthorized access, and exfiltrate sensitive data from the target network.

- The official CVE entry for the vulnerability: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-25234
- Omnissa's security advisory regarding the issue: https://www.omnissa.com/security/advisories/CVE-2025-25234
- A detailed technical explanation of the CORS bypass vulnerability: https://www.owasp.org/index.php/Cross-Origin_Resource_Sharing_Cheat_Sheet#CORS_Bypasses

To exploit the CVE-2025-25234 vulnerability, an attacker must follow these steps

1. The attacker must have network access to the Omnissa UAG. This can be achieved via various network scanning and reconnaissance techniques.

2. Utilizing a website or web app under their control, attackers can craft malicious code (e.g., the JavaScript code snippet provided above) that performs CORS bypass attacks targeting the Omnissa UAG.

3. The attacker aims to trick administrators or users into visiting the malicious website or web app by employing social engineering tactics such as phishing emails, malicious advertisements, or compromised legitimate websites.

4. When the victim accesses the malicious website or web app, the JavaScript code is executed within the context of their web browser, and the malicious requests are sent to the Omnissa UAG, bypassing the CORS restrictions.

5. If successful, the attacker will gain access to sensitive information or execute arbitrary actions within the protected network.

Conclusion

The CVE-2025-25234 Omnissa UAG CORS bypass vulnerability poses a significant security risk to organizations that rely on this platform to protect their networks. It is critical for administrators to apply the necessary security patches and updates as soon as they become available, to prevent potential exploitation of this vulnerability by malicious actors. Moreover, security awareness training and best practices should be emphasized to minimize the chances of falling victim to social engineering attacks.

Timeline

Published on: 04/17/2025 15:15:54 UTC
Last modified on: 04/21/2025 18:35:58 UTC