CVE-2026-17781 in Chrome
Summary
by MITRE • 07/30/2026
Inappropriate implementation in Extensions in Google Chrome prior to 151.0.7922.72 allowed an attacker who convinced a user to install a malicious extension to leak cross-origin data 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 authorization and data leakage flaw within the chrome extension architecture that existed in versions prior to 151.0.7922.72. The issue stems from insufficient validation mechanisms in the extension installation and execution pipeline, allowing malicious actors to exploit trust relationships between browser components and external domains. The vulnerability specifically targets the cross-origin data access controls that should normally prevent extensions from reading or transmitting information from different origins than those they were designed to interact with.
The technical implementation flaw manifests as a failure in the chrome extension security model where the browser does not properly enforce origin restrictions when processing malicious extensions. This allows attackers to craft extensions that can bypass normal security boundaries and access data from unrelated domains, effectively creating a cross-origin information disclosure vector. The vulnerability operates through the extension installation process where a user is tricked into installing a seemingly legitimate extension that contains malicious code designed to harvest sensitive information from other websites or browser contexts.
From an operational perspective this vulnerability enables sophisticated phishing campaigns and targeted attacks where adversaries can leverage social engineering tactics to convince users to install extensions that appear benign but contain hidden capabilities for cross-origin data exfiltration. The medium severity classification according to chromium security guidelines reflects the potential for significant privacy violations and data breaches when exploited in real-world scenarios. Attackers could potentially harvest cookies, session tokens, personal information, or other sensitive data from multiple domains without user knowledge, particularly targeting high-value targets such as financial institutions, government agencies, or corporate environments.
The attack vector relies heavily on user deception through social engineering techniques combined with the exploitation of trust relationships within the chrome extension ecosystem. This vulnerability aligns with several ATT&CK framework techniques including initial access through malicious extensions and credential access through session hijacking. The flaw represents a specific implementation gap that should have been addressed through proper input validation and origin enforcement mechanisms as defined in common weakness enumeration standards such as CWE-20 for improper input validation and CWE-284 for improper access control.
Mitigation strategies should focus on immediate browser updates to versions 151.0.7922.72 and later, where the security implementation has been corrected to properly enforce cross-origin restrictions. Organizations should also implement extension management policies that limit which extensions can be installed and regularly audit installed extensions for suspicious behavior patterns. Additional protective measures include implementing content security policies, monitoring for unusual extension activity, and conducting regular security awareness training to help users identify potentially malicious extension requests. The fix typically involves strengthening the chrome extension permission model and ensuring that all cross-origin data access requests undergo proper validation against the extension's declared permissions and origin boundaries.