CVE-2025-5263 in Firefox
Summary
by MITRE • 05/27/2025
Error handling for script execution was incorrectly isolated from web content, which could have allowed cross-origin leak attacks. This vulnerability affects Firefox < 139, Firefox ESR < 115.24, and Firefox ESR < 128.11.
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Analysis
by VulDB Data Team • 08/16/2025
This vulnerability represents a critical cross-origin information disclosure flaw in Mozilla Firefox browsers that stems from improper isolation of script execution error handling mechanisms from web content contexts. The issue arises when error messages generated during script execution contain sensitive cross-origin data that should remain isolated from potentially malicious web pages. When error handling routines fail to properly sanitize or isolate their output, they can inadvertently expose information about cross-origin resources, including URLs, resource identifiers, or other contextual data that could be leveraged by attackers to reconstruct sensitive information about user browsing sessions or network configurations.
The technical implementation flaw manifests in how Firefox processes and displays error messages when scripts encounter execution failures. Specifically, the error handling subsystem does not sufficiently separate the execution context of scripts from the web content rendering environment, allowing error data to leak across origin boundaries. This misconfiguration enables attackers to craft malicious web pages that can trigger specific script execution scenarios, causing error messages to contain cross-origin information that would normally be protected by browser security policies. The vulnerability affects multiple Firefox versions including Firefox 138 and earlier, Firefox ESR 115.23 and earlier, and Firefox ESR 128.10 and earlier, indicating a widespread impact across both regular release cycles and extended support branches.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable sophisticated cross-origin attacks that bypass traditional security boundaries. Attackers can exploit this weakness to perform cross-origin resource leakage, potentially reconstructing user session information, identifying internal network resources, or mapping cross-origin relationships that would normally remain hidden. This type of vulnerability directly impacts the browser's same-origin policy implementation and can undermine the fundamental security model that protects users from malicious cross-origin interactions. The attack vector typically involves crafting malicious web content that triggers specific error conditions in script execution, causing the browser to leak cross-origin information through error messages that are then accessible to the attacking page.
Security mitigations for this vulnerability require immediate updates to affected Firefox versions, with administrators prioritizing deployment of Firefox 139, Firefox ESR 115.24, or Firefox ESR 128.11 releases that contain the necessary fixes. The patch addresses the core issue by implementing proper isolation mechanisms between script execution error handling and web content rendering contexts, ensuring that error messages cannot contain cross-origin information. Organizations should also consider implementing additional network-level protections such as content security policies and strict origin validation measures to reduce the potential impact of any remaining vulnerabilities. This vulnerability aligns with CWE-200 (Information Exposure) and can be classified under ATT&CK technique T1557 (Adversary-in-the-Middle) when used in conjunction with other attack vectors. The fix demonstrates the importance of maintaining strict separation between execution contexts in browser security implementations and highlights the critical nature of proper error handling in preventing information leakage attacks that can compromise user privacy and system integrity.