CVE-2017-5045 in Chrome
Summary
by MITRE
XSS Auditor in Google Chrome prior to 57.0.2987.98 for Mac, Windows, and Linux and 57.0.2987.108 for Android allowed detection of a blocked iframe load, which allowed a remote attacker to brute force JavaScript variables via a crafted HTML page.
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Analysis
by VulDB Data Team • 12/02/2022
The vulnerability identified as CVE-2017-5045 represents a significant security flaw in Google Chrome's XSS Auditor implementation that affected multiple platform versions. This weakness specifically targeted the browser's mechanism designed to prevent cross-site scripting attacks, creating an unintended information disclosure channel that could be exploited by remote attackers. The vulnerability emerged from the XSS Auditor's inability to properly handle iframe load detection, allowing malicious actors to infer the presence of blocked content through indirect means. This flaw existed across Chrome versions 57.0.2987.98 for Mac, Windows, and Linux platforms, as well as version 57.0.2987.108 for Android devices, indicating a widespread impact across the browser's major operating system variants.
The technical exploitation of this vulnerability stems from the XSS Auditor's design flaw where it would reveal information about blocked iframe loads to remote attackers through timing variations and other indirect detection methods. When Chrome's XSS Auditor blocked certain iframe content, the browser would still provide observable side effects that could be monitored by attackers. This occurred because the auditor's detection mechanism was not sufficiently robust to prevent information leakage through the timing differences between blocked and allowed content loading. Attackers could leverage this behavior to perform brute force attacks against JavaScript variables by observing these timing variations and indirect indicators of content blocking. The flaw essentially allowed attackers to determine whether specific JavaScript variables were present or absent in blocked iframe content, creating a covert channel for information extraction.
The operational impact of CVE-2017-5045 extends beyond simple information disclosure, as it enabled sophisticated attack vectors that could compromise user privacy and application security. Remote attackers could exploit this vulnerability to reconstruct sensitive JavaScript variable values through systematic brute force techniques, potentially exposing session tokens, application state variables, or other confidential data. This capability significantly weakened Chrome's security posture and undermined the trust users placed in the browser's XSS protection mechanisms. The vulnerability's impact was particularly concerning because it affected the core security feature designed to protect against cross-site scripting attacks, creating a scenario where the very mechanism meant to prevent malicious code execution could be subverted to reveal information about blocked content. The flaw created a paradoxical security issue where the protection mechanism itself became a vector for information leakage.
The vulnerability aligns with CWE-200, which describes "Information Exposure," and demonstrates how security controls can inadvertently create new attack surfaces when not properly designed to prevent all forms of information leakage. From an ATT&CK perspective, this vulnerability maps to techniques involving information gathering and reconnaissance, specifically targeting the discovery of application state and variable information through indirect means. The exploitation pattern corresponds to T1212, "Exploitation for Credential Access," as the ability to brute force JavaScript variables could lead to credential exposure or session hijacking. Organizations should have implemented immediate mitigations including upgrading to Chrome versions 57.0.2987.98 or later for affected platforms, as well as implementing additional network-level protections such as content security policies to reduce the attack surface. Browser vendors and security teams should have prioritized this vulnerability due to its potential for enabling more sophisticated attacks beyond simple information disclosure, emphasizing the importance of comprehensive security review processes that consider all possible side channels in security mechanisms.