CVE-2026-121040 in Chrome
Summary
by MITRE • 11/03/2026
Incorrect authorization in Core in Google Chrome prior to 157.0.8103.38 allowed a remote attacker who had compromised the renderer process to bypass system access restrictions via a crafted HTML page. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified as an incorrect authorization flaw within the core components of Google Chrome prior to version 157.0.8103.38 represents a significant breach in process isolation boundaries, which are fundamental to modern browser security architectures. This issue specifically affects the renderer processes that handle web content execution. In standard Chromium-based browsers, each tab or frame typically runs in its own sandboxed renderer process with restricted permissions to prevent malicious code from accessing sensitive system resources or other tabs. The flaw arises when these isolation mechanisms fail to properly validate authorization checks for specific operations initiated by a compromised renderer. This failure allows an attacker who has already achieved execution within the renderer environment through initial exploitation vectors such as cross-site scripting or drive-by downloads to escalate privileges beyond the intended sandbox constraints.
From a technical perspective, this vulnerability aligns with CWE-269, which describes Improper Privilege Management, and more specifically relates to issues where access control decisions are not enforced correctly during runtime operations. The attacker leverages a crafted HTML page designed to trigger specific API calls or internal browser functions that bypass the expected permission checks. By exploiting this logic error in the authorization flow, the malicious code can interact with system-level interfaces or sensitive data stores that should remain inaccessible from within the renderer sandbox. This effectively neutralizes one of the primary defense layers against remote code execution attacks, allowing the attacker to perform actions such as reading local files, accessing browser history, or potentially interacting with other open tabs depending on the specific implementation details of the bypassed restriction.
The operational impact of this vulnerability is severe for users who visit maliciously crafted web pages while using an affected version of Chrome. Although the initial entry point requires compromising a renderer process, which often involves exploiting additional vulnerabilities in JavaScript engines or plugins, the subsequent privilege escalation significantly increases the attack surface and potential damage. An attacker could use this capability to exfiltrate sensitive user data stored locally by the browser, such as cookies containing session tokens, cached credentials, or personal information saved in forms. Furthermore, if combined with other techniques like phishing or social engineering, this flaw facilitates more sophisticated persistent access scenarios where the malicious actor maintains control over the victim's browsing environment without triggering typical security alerts associated with sandbox escapes.
Mitigation strategies primarily involve immediate software updates to address the underlying code defects responsible for the authorization bypass. Users and administrators must upgrade Google Chrome to version 157.0.8103.38 or later, where these access control checks have been hardened and validated against known exploitation patterns. In environments where patching cannot be applied immediately due to compatibility concerns, network-level controls such as web filtering proxies can help block traffic from domains exhibiting characteristics of exploit delivery infrastructure. Additionally, enabling strict content security policies for internal applications hosted on Chrome-based browsers can reduce the likelihood of initial renderer compromise. Security teams should also monitor endpoint detection and response systems for unusual process behavior indicative of sandbox escape attempts, aligning with MITRE ATT&CK techniques related to privilege escalation and defense evasion within browser contexts.