CVE-2026-17821 in Chrome
Summary
by MITRE • 07/30/2026
Insufficient policy enforcement in Extensions in Google Chrome prior to 151.0.7922.72 allowed an attacker who convinced a user to install a malicious extension to bypass navigation restrictions via a crafted Chrome Extension. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 07/30/2026
This vulnerability represents a critical flaw in chrome's extension permission model that existed prior to version 151.0.7922.72, allowing attackers to circumvent navigation restrictions through malicious extension installation. The issue stems from insufficient policy enforcement mechanisms within chrome's extension architecture, specifically affecting how the browser handles extension permissions and navigation controls. Attackers could exploit this weakness by crafting a malicious extension that would appear legitimate to users while secretly bypassing established security boundaries. The vulnerability falls under the category of privilege escalation through extension manipulation, with implications for user privacy and system integrity.
The technical flaw manifests in chrome's failure to properly validate extension permissions against established navigation policies during runtime execution. When users install extensions, chrome should enforce strict policy checks that prevent malicious code from altering navigation behavior or accessing restricted resources. However, this vulnerability allowed attackers to bypass these validation mechanisms, enabling extensions to manipulate browser navigation flows without proper authorization. The flaw likely existed in how chrome's extension sandboxing processes interacted with navigation controls, creating a pathway for unauthorized access to restricted browsing functions. This type of vulnerability typically maps to CWE-284 Access Control Issues within the Common Weakness Enumeration framework, specifically concerning improper access control enforcement.
The operational impact of this vulnerability extends beyond simple navigation bypasses, potentially enabling sophisticated phishing attacks, data exfiltration, and user tracking activities. An attacker could craft extensions that redirect users to malicious sites while maintaining the appearance of legitimate browsing behavior, making detection extremely difficult. Users might unknowingly grant permissions to extensions that appear safe but contain hidden malicious functionality designed specifically to exploit this policy enforcement weakness. The medium severity rating reflects the significant risk this vulnerability posed to user security and privacy, particularly in environments where chrome is used for sensitive activities such as online banking or corporate data access.
Mitigation strategies should focus on immediate chrome updates to version 151.0.7922.72 or later, which would address the underlying policy enforcement issues. Organizations should implement strict extension management policies that require thorough vetting before installation and maintain regular monitoring of installed extensions. Users must be educated about extension permissions and encouraged to only install software from trusted sources. Additionally, administrators should consider implementing browser security policies that restrict extension installation capabilities and monitor for suspicious navigation patterns. This vulnerability highlights the importance of maintaining up-to-date browsers and proper access control mechanisms. The issue also aligns with ATT&CK technique T1176 Browser Extensions, emphasizing how malicious extensions can be used to establish persistent access and bypass security controls within web browsing environments. Regular security audits of installed extensions and implementation of automated extension management systems would significantly reduce the risk of exploitation.