CVE-2018-8366 in Edge
Summary
by MITRE
An information disclosure vulnerability exists when the Microsoft Edge Fetch API incorrectly handles a filtered response type, aka "Microsoft Edge Information Disclosure Vulnerability." This affects Microsoft Edge.
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Analysis
by VulDB Data Team • 05/08/2023
The CVE-2018-8366 vulnerability represents a critical information disclosure flaw within Microsoft Edge browser's implementation of the Fetch API specification. This vulnerability arises from the improper handling of filtered response types during cross-origin requests, creating a potential avenue for attackers to access sensitive data that should remain restricted. The flaw specifically manifests when the browser's Fetch API processes responses that undergo filtering mechanisms, allowing unauthorized data exposure through manipulated request sequences.
The technical root cause of this vulnerability stems from the Fetch API's inadequate validation of response filtering behaviors in cross-origin scenarios. When Microsoft Edge encounters a response that should be filtered due to CORS (Cross-Origin Resource Sharing) restrictions, the implementation fails to properly enforce these security boundaries. This misconfiguration enables attackers to craft malicious requests that can bypass expected security controls, potentially exposing cookies, authentication tokens, or other sensitive information from different origins. The vulnerability operates at the intersection of web standards implementation and security boundary enforcement, where the browser's interpretation of CORS policies becomes inconsistent with the intended security model.
From an operational impact perspective, this vulnerability poses significant risks to user privacy and application security within Microsoft Edge environments. Attackers could leverage this flaw to perform cross-origin information leakage attacks, potentially accessing session tokens, personal data, or enterprise information from legitimate web applications. The attack vector typically involves crafting specific fetch requests that exploit the filtering mechanism's weakness, allowing data from restricted origins to be accessed through the browser's API. This creates a persistent threat vector that could affect any web application relying on Edge browser for user interactions, particularly those handling sensitive data or implementing authentication mechanisms.
Security professionals should consider this vulnerability in the context of the CWE-200 information disclosure weakness category, which encompasses improper restriction of information exposure. The ATT&CK framework categorizes this as a privilege escalation or information gathering technique, potentially enabling more sophisticated attacks through data reconnaissance. Organizations should prioritize patching this vulnerability through Microsoft's security updates, while implementing additional monitoring for suspicious fetch API usage patterns. Network security controls should also be configured to detect anomalous cross-origin requests that might indicate exploitation attempts, particularly those involving the specific filtering scenarios that trigger this vulnerability. The remediation process requires careful attention to ensure that browser updates are deployed consistently across all affected systems while maintaining proper security posture through additional defensive measures.