CVE-2025-8031 in Thunderbird
Summary
by MITRE • 07/23/2025
The `username:password` part was not correctly stripped from URLs in CSP reports potentially leaking HTTP Basic Authentication credentials. This vulnerability affects Firefox < 141, Firefox ESR < 128.13, Firefox ESR < 140.1, Thunderbird < 141, Thunderbird < 128.13, and Thunderbird < 140.1.
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Analysis
by VulDB Data Team • 08/08/2025
The vulnerability identified as CVE-2025-8031 represents a critical security flaw in Mozilla Firefox and Thunderbird browsers related to how they handle Cross-Site Scripting (CSP) reports. This issue stems from improper URL parsing where the username and password components of HTTP Basic Authentication credentials remain intact within CSP violation reports, creating a potential exposure vector for sensitive authentication data. The flaw specifically impacts versions prior to Firefox 141 and its Extended Support Release versions, as well as Thunderbird versions up to 141 and its corresponding ESR releases.
The technical implementation of this vulnerability occurs within the browser's Content Security Policy reporting mechanism. When a web application generates a CSP violation report, the browser includes the full URL from which the violation originated. However, in cases where the URL contains embedded HTTP Basic Authentication credentials in the format username:[email protected], the authentication portion is not properly sanitized or stripped from the report. This behavior violates fundamental security principles for handling sensitive information in log data and reporting mechanisms.
From an operational perspective, this vulnerability creates significant risk for organizations relying on HTTP Basic Authentication for web applications. An attacker who can intercept CSP violation reports could extract authentication credentials from URLs, potentially gaining unauthorized access to protected resources. The impact extends beyond simple credential leakage as these credentials could be used to access other systems or services that share the same authentication mechanisms. This vulnerability particularly affects environments where CSP is actively implemented and where applications use HTTP Basic Authentication for access control.
The security implications of CVE-2025-8031 align with CWE-200 (Information Exposure) and CWE-532 (Information Exposure Through Log Data) categories, as the flaw directly enables unauthorized information disclosure through log and report mechanisms. This vulnerability also maps to ATT&CK technique T1566 (Phishing) and T1071.004 (Application Layer Protocol: DNS) when considering how attackers might leverage credential exposure for further attacks. The flaw demonstrates poor input validation and sanitization practices in the browser's URL handling components, specifically within the CSP reporting subsystem.
Organizations should immediately update to the patched versions of Firefox and Thunderbird to mitigate this vulnerability. System administrators should also review CSP configurations to ensure that sensitive URLs are not being exposed through violation reports. Network monitoring should be enhanced to detect unusual patterns in CSP report traffic that might indicate credential leakage. Additionally, security teams should implement regular audits of authentication mechanisms to ensure that HTTP Basic Authentication is not being used in environments where it could expose credentials through report mechanisms. The vulnerability underscores the importance of proper URL sanitization in all browser components and highlights the need for comprehensive security testing of reporting and logging functionalities in web browsers.