CVE-2024-6612 in Firefox
Summary
by MITRE • 07/09/2024
CSP violations generated links in the console tab of the developer tools, pointing to the violating resource. This caused a DNS prefetch which leaked that a CSP violation happened. This vulnerability affects Firefox < 128.
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Analysis
by VulDB Data Team • 03/20/2025
This vulnerability in Firefox versions prior to 128 represents a sophisticated information disclosure issue that exploits the browser's developer tools functionality to reveal security policy violations. The flaw manifests when Content Security Policy (CSP) violations occur within web applications, causing the browser to generate clickable links in the console tab of developer tools that point to the violating resources. These links trigger automatic DNS prefetching behavior in the browser, creating an indirect method for adversaries to detect when CSP violations have occurred. The vulnerability stems from the improper handling of CSP violation reporting within the browser's debugging interface, where the mere presence of these links activates network resolution processes that can be monitored by external parties.
The technical implementation of this vulnerability involves the interaction between Firefox's CSP enforcement mechanisms and its developer tools console functionality. When a CSP policy is violated, Firefox's console displays a message containing a hyperlink to the violating resource, which is designed for debugging purposes to allow developers to quickly access problematic content. However, the browser's automatic DNS prefetching behavior is triggered when these links are rendered, even in the developer tools context. This DNS prefetching creates network traffic patterns that can be observed by network monitoring tools, providing an indirect channel for information leakage about the presence of security policy violations.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can be exploited to determine whether specific web applications are running CSP policies and to identify potential attack vectors. An attacker monitoring network traffic can observe DNS queries triggered by these prefetching mechanisms to infer when CSP violations occur, potentially revealing information about application security configurations and user interactions with web content. This type of information leakage can be particularly dangerous in environments where CSP policies are used to protect against cross-site scripting attacks and other client-side threats, as it provides adversaries with insights into the effectiveness of security controls and potential areas of weakness.
This vulnerability aligns with CWE-200, which addresses information exposure, and represents a specific case of information leakage through unintended side effects of browser functionality. The flaw demonstrates how seemingly innocuous developer tools features can create security implications when combined with network behavior patterns. From an ATT&CK perspective, this vulnerability relates to techniques involving reconnaissance and information gathering, specifically T1592 for reconnaissance and T1590 for reconnaissance through network traffic analysis. The attack vector leverages the browser's developer tools as an entry point for indirect information disclosure, making it particularly concerning for applications where CSP is used as a security control.
Mitigation strategies for this vulnerability require updating Firefox to version 128 or later, where the issue has been addressed through modifications to how developer tools handle CSP violation links and the elimination of automatic DNS prefetching for these resources. Organizations should also consider implementing network monitoring to detect unusual DNS query patterns that might indicate exploitation attempts. Additionally, developers should be aware that CSP violations should not be relied upon as the sole indicator of security issues, as this vulnerability demonstrates that such violations can be detected through alternative means. The fix implemented by Mozilla likely involved disabling automatic DNS prefetching for links generated in the developer tools console or modifying the link generation mechanism to prevent triggering network resolution behavior.