CVE-2026-78967 in Chrome
Summary
by MITRE • 08/25/2026
Missing authorization in BFCache in Google Chrome prior to 152.0.7977.65 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 • 08/25/2026
The vulnerability identified as missing authorization within the BFCache mechanism of Google Chrome prior to version 152.0.7977.65 represents a significant breach in process isolation and access control logic. The Back-Forward Cache, or BFCache, is an optimization feature designed to improve navigation performance by caching entire pages rather than just their network resources. When a user navigates away from a page and then returns using the browser's back or forward buttons, Chrome can restore the previous state instantly without re-fetching data from the server. However, this mechanism relies heavily on strict security boundaries between different execution contexts within the browser architecture. In this specific instance, the authorization checks required to validate whether a renderer process should have access to cached content were insufficiently enforced. This oversight creates a pathway for privilege escalation where a compromised renderer can interact with sensitive data or states that it should not be able to access under normal circumstances.
From a technical perspective, Chrome operates on a multi-process architecture where each tab and plugin runs in an isolated sandboxed environment known as the renderer process. The primary security goal is to ensure that if one renderer is compromised by malicious code, such as through a cross-site scripting attack or drive-by download, the attacker cannot escape this sandbox to access other tabs, browser internals, or system resources. The BFCache stores snapshots of page states, including DOM trees and JavaScript heap contents, in memory for rapid restoration. When authorization checks are missing during the retrieval or storage phase within this cache, a malicious actor who has already achieved code execution inside one renderer process can craft an HTML payload that exploits this gap. By leveraging specific navigation sequences or state manipulations, the attacker can trick the browser into granting access to cached data belonging to other origins or privileged contexts, effectively bypassing the same-origin policy and system-level access restrictions designed to contain threats within individual tabs.
The operational impact of this vulnerability is substantial because it undermines the fundamental trust model of web browsers. An attacker who successfully exploits this flaw can potentially read sensitive information from other open tabs, such as session tokens, personal data, or confidential application states that were cached by BFCache. This capability transforms a contained renderer compromise into a broader security incident affecting multiple browsing sessions and user privacy. The severity is classified as medium because while it allows for significant data exfiltration and context switching between origins, it typically requires the initial foothold of compromising a renderer process first. Nevertheless, given that many modern web applications rely on client-side caching for performance and state management, this vulnerability poses a risk to any user who keeps multiple tabs open with sensitive content, as the cached states remain accessible in memory even after navigation away from those pages if not properly cleared or secured.
This flaw aligns closely with CWE-269, which describes Improper Privilege Assignment, specifically where an actor is granted privileges that exceed their intended role within the system architecture. Furthermore, it relates to ATT&CK technique T1053, Scheduled Task/Job, in a broader sense of abusing scheduled or cached operations for persistence and access, though more accurately it maps to lateral movement techniques such as T1210, Exploitation of Remote Services, if viewed through the lens of moving between isolated contexts. The exploitation vector is classified as remote because the initial trigger can be delivered via a crafted HTML page hosted on a malicious website or embedded in an advertisement network. Once loaded and executed within the victim's browser environment, the exploit does not require user interaction beyond visiting the site, making it particularly dangerous for users who may inadvertently navigate to compromised pages while browsing sensitive services like banking portals or email clients that utilize BFCache optimizations.
Mitigation strategies primarily involve updating Google Chrome to version 152.0.7977.65 or later, where these authorization checks have been rigorously enforced within the BFCache implementation. For organizations managing large fleets of endpoints, ensuring automatic update policies are in place is critical to prevent exposure during the window between vulnerability disclosure and patch deployment. Additionally, security teams should monitor for unusual memory access patterns from renderer processes that deviate from standard navigation flows, although this may be challenging due to the complexity of browser internals. Users can also mitigate risk by disabling BFCache if they operate in high-security environments where performance gains are less critical than strict isolation guarantees, though this is generally not recommended for general use due to significant usability impacts. Regular security audits and penetration testing that simulate renderer escapes should include checks against cache-related state leakage to ensure robust defense-in-depth measures remain effective against evolving browser-based attack vectors.