CVE-2026-106336 in Chrome
Summary
by MITRE • 10/07/2026
Observable discrepancy in Paint in Google Chrome prior to 155.0.8059.39 allowed a remote attacker to leak cross-origin data via a crafted HTML page. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 10/07/2026
The vulnerability identified as an observable discrepancy in the rendering engine of Google Chrome, specifically affecting versions prior to 155.0.8059.39, represents a significant breach in cross-origin isolation principles. This flaw resides within the Paint subsystem, which is responsible for compositing and displaying visual elements on the user interface. The core technical issue stems from an improper handling of rendering state or timing conditions that allow information to persist across security boundaries where it should be strictly isolated. By crafting a specific HTML page containing malicious scripts and carefully timed DOM manipulations, an attacker can exploit this discrepancy to infer data belonging to other origins. This is not a direct extraction of raw memory but rather a side-channel attack that leverages visual artifacts or rendering timing differences to deduce sensitive information such as layout dimensions, content presence, or specific style properties from cross-origin iframes or windows.
From a technical perspective, this vulnerability aligns with CWE-200, which classifies it as an Information Exposure vulnerability where security-sensitive information is disclosed without explicit authorization. The mechanism relies on the browser's failure to properly sanitize or randomize rendering outputs when dealing with mixed content scenarios involving different origins. In modern web architectures, browsers enforce strict same-origin policies to prevent scripts from accessing data across domains. However, when the Paint engine processes elements that span these boundaries, a race condition or state leakage can occur. The attacker constructs an environment where they control one origin and attempt to observe rendering behaviors of another origin. By measuring pixel values, layout shifts, or frame rates associated with the target content, the malicious script can reconstruct data bits byte by bit. This technique is sophisticated because it bypasses traditional memory safety checks by exploiting high-level application logic errors in the graphics pipeline rather than low-level buffer overflows.
The operational impact of this vulnerability allows a remote attacker to conduct cross-origin information leakage attacks against users browsing with affected versions of Chrome. If a user visits a malicious webpage while simultaneously having sensitive web applications open in other tabs or iframes, such as online banking portals, email services, or corporate intranets, the attacker can potentially exfiltrate private data. This could include identifying specific elements on a page, determining which features are enabled based on layout changes, or even reconstructing text content through subtle visual cues. The severity is rated as Medium by Chromium because while it does not allow for arbitrary code execution or direct system compromise, it undermines the fundamental trust model of the web browser. It enables surveillance-like capabilities where an attacker can monitor user activity and extract sensitive context without the user's knowledge, leading to potential privacy violations and data breaches that could be leveraged for further social engineering or targeted attacks.
Mitigation strategies primarily involve updating the Google Chrome browser to version 155.0.8059.39 or later, where this rendering discrepancy has been corrected through improved isolation of paint operations across origin boundaries. For organizations unable to immediately patch all endpoints, implementing strict Content Security Policy (CSP) headers can help mitigate some risks by restricting the sources from which scripts and resources are loaded, thereby reducing the attack surface for crafted HTML pages. Additionally, enabling features like Cross-Origin Opener Policy (COOP) and Cross-Origin Embedder Policy (COEP) enhances isolation between browsing contexts, making it significantly harder for an attacker to observe cross-origin rendering states. Users should also be educated about the risks of visiting untrusted websites while engaged in sensitive online activities, as this vulnerability exploits the coexistence of malicious and legitimate content within the same browser session environment.
In terms of threat intelligence frameworks, this activity corresponds to ATT&CK technique T1056, specifically sub-technique 004 which covers Input Capture via Keylogging or Screen Scraping, although in this context it is more accurately described as a form of side-channel information gathering akin to T1078 Valid Accounts if used for session hijacking after data extraction. It also relates to the broader category of browser-based attacks where the attacker abuses legitimate system functionality to achieve unauthorized access to information. The fix ensures that the Paint engine correctly isolates rendering contexts, preventing any leakage of visual state that could be correlated with cross-origin content. Maintaining up-to-date software is critical as these types of logic flaws in complex engines like Blink are often discovered and patched rapidly by security researchers who continuously probe for such discrepancies in web standards compliance and isolation enforcement mechanisms.