CVE-2021-38017 in Chrome
Summary
by MITRE • 12/23/2021
Insufficient policy enforcement in iframe sandbox in Google Chrome prior to 96.0.4664.45 allowed a remote attacker to bypass navigation restrictions via a crafted HTML page.
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Analysis
by VulDB Data Team • 12/26/2021
The vulnerability identified as CVE-2021-38017 represents a critical weakness in Google Chrome's implementation of iframe sandboxing mechanisms that persisted across multiple versions prior to the 96.0.4664.45 release. This flaw specifically targets the browser's security model designed to isolate potentially malicious content within sandboxed iframes, creating a pathway for remote attackers to circumvent intended navigation restrictions. The issue manifests when a crafted HTML page exploits insufficient policy enforcement within the sandbox environment, allowing unauthorized navigation attempts that should have been blocked by security controls.
The technical root cause of this vulnerability lies in the inadequate validation and enforcement of security policies within Chrome's iframe sandbox implementation. When a webpage attempts to create an iframe with sandbox attributes, the browser should enforce strict restrictions on navigation capabilities to prevent malicious actors from redirecting users to harmful destinations. However, this vulnerability demonstrates that Chrome's enforcement mechanism failed to properly validate navigation requests originating from sandboxed contexts, enabling attackers to bypass these protective measures through carefully constructed HTML content. The flaw operates at the intersection of web security standards and browser implementation, where the expected behavior of sandboxed environments was not consistently enforced.
The operational impact of this vulnerability extends beyond simple navigation bypasses and represents a significant threat to user security and privacy. Remote attackers could leverage this weakness to redirect users to phishing sites, malicious domains, or exploit other web-based vulnerabilities by manipulating iframe navigation behavior. This capability undermines the fundamental security assumptions that users and developers rely upon when implementing sandboxed content, potentially enabling more sophisticated attack vectors including cross-site scripting exploitation, credential harvesting, or delivery of malicious payloads. The vulnerability particularly affects users who encounter crafted web pages in contexts where iframe sandboxing is expected to provide protection.
Security practitioners should implement immediate mitigations including prompt browser updates to Chrome version 96.0.4664.45 or later, which contains the necessary patches to address the policy enforcement gap. Organizations should also consider implementing additional monitoring for suspicious navigation patterns within sandboxed environments and review their web application security policies to ensure proper sandbox attribute usage. This vulnerability aligns with CWE-693, which addresses Protection Mechanism Failure, and maps to ATT&CK technique T1211, related to Exploitation for Defense Evasion, as attackers could use this bypass to maintain persistence or evade security controls. The remediation strategy should include comprehensive browser security assessments and regular vulnerability scanning to identify similar policy enforcement weaknesses across the organization's browser-based applications.