CVE-2026-121063 in Chrome
Summary
by MITRE • 11/03/2026
Incorrect authorization in CacheStorage in Google Chrome prior to 157.0.8103.38 allowed a remote attacker who had compromised the renderer process to bypass site isolation 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 CacheStorage component of Google Chrome prior to version 157.0.8103.38 represents a significant breach in the browser's multi-process architecture integrity. This issue specifically targets the mechanism that manages cached web resources, allowing for unauthorized access patterns when combined with other compromised states. The core technical flaw lies in the insufficient validation of permissions associated with cache entries during retrieval or manipulation operations. When an attacker successfully compromises the renderer process through a separate vector such as cross-site scripting or another remote code execution exploit, they gain the ability to interact with the CacheStorage API. Under normal circumstances, this interaction is strictly bound by origin-based security policies designed to isolate data between different websites. However, due to the authorization error, these boundaries become permeable, enabling the attacker to read or modify cache entries belonging to other origins that should remain inaccessible from the compromised renderer context.
This flaw directly facilitates a bypass of site isolation, a critical defense mechanism in modern web browsers intended to prevent cross-site data leakage and mitigate certain classes of side-channel attacks like Spectre. Site isolation ensures that each website runs in its own process with dedicated memory space, preventing one tab or origin from accessing the private state of another. By exploiting this CacheStorage authorization issue, an attacker can effectively bridge these isolated environments. The operational impact is severe because it allows a remote attacker to escalate privileges within the browser's security model without requiring additional local exploits. Once site isolation is bypassed, the attacker gains access to sensitive information stored in cache entries across different origins, potentially including authentication tokens, session identifiers, or other confidential user data that was cached for performance optimization purposes.
From an industry standards perspective, this vulnerability aligns with CWE-269, which describes Improper Privilege Assignment, as it involves a failure to enforce the correct level of access control on system resources. Furthermore, the exploitation technique maps closely to MITRE ATT&CK techniques related to Defense Evasion and Credential Access, specifically those involving browser security bypasses and unauthorized data exfiltration via web application components. The ability to traverse origin boundaries undermines the fundamental trust model of the web platform, making it easier for attackers to conduct sophisticated phishing campaigns or session hijacking attacks by leveraging cached credentials that were not intended to be visible outside their original context.
Mitigation strategies primarily involve updating Google Chrome to version 157.0.8103.38 or later, where these authorization checks have been hardened and validated against cross-origin access attempts. For organizations unable to patch immediately, implementing strict Content Security Policy directives can help limit the execution of untrusted scripts that might attempt to leverage CacheStorage APIs for malicious purposes. Additionally, disabling caching for sensitive pages through HTTP headers such as Cache-Control: no-store reduces the attack surface by ensuring that high-value data is not persisted in a manner susceptible to this specific authorization flaw. Regular security audits focusing on web storage usage patterns and adherence to least-privilege principles within application code can further reduce the risk of exploitation should similar vulnerabilities arise in future browser versions.