CVE-2026-103621 in Chrome
Summary
by MITRE • 10/02/2026
Integer overflow in Compositing in Google Chrome prior to 154.0.8037.97 allowed a remote attacker to leak cross-origin data via a crafted HTML page. (Chromium security severity: High)
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 10/02/2026
The vulnerability identified as an integer overflow within the compositing subsystem of Google Chrome represents a critical failure in memory management and bounds checking during the rendering pipeline. This specific flaw occurs when calculating dimensions or offsets for visual elements, where arithmetic operations exceed the maximum value representable by the allocated data type, leading to wrap-around behavior. In the context of browser architecture, the compositor is responsible for assembling layers into final images displayed on screen. When an integer overflow manipulates these calculations, it can result in incorrect memory access patterns or buffer overruns that bypass standard security boundaries. This technical flaw allows a remote attacker to exploit the discrepancy between expected and actual memory addresses, facilitating unauthorized read operations across origin boundaries.
From a functional perspective, this vulnerability enables cross-origin data leakage, which is a severe breach of the Same-Origin Policy (SOP). The SOP is a fundamental security concept that restricts how documents or scripts loaded from one origin can interact with resources from another origin. By leveraging the integer overflow in compositing, an attacker can craft a malicious HTML page that tricks the browser into rendering content in a way that exposes sensitive data belonging to other domains. This could include cookies, local storage contents, or dynamic web application data that should remain isolated within their respective origins. The ability to exfiltrate this information undermines user privacy and compromises the integrity of web applications relying on origin isolation for security.
The operational impact of this vulnerability is significant, particularly given its remote exploitability via a crafted HTML page. Users visiting malicious websites or being redirected through compromised advertising networks could trigger the flaw without any additional interaction beyond loading the page. The Chromium project has classified this issue with high severity due to the potential for widespread data theft and the relative ease with which it can be weaponized in phishing campaigns or drive-by download attacks. Successful exploitation allows attackers to build profiles of user activity, steal session tokens, or inject malicious scripts into trusted contexts by reading sensitive cross-origin resources that were previously inaccessible.
Mitigation strategies primarily involve updating Google Chrome to version 154.0.8037.97 or later, where the integer overflow in the compositing logic has been patched with proper bounds checking and type-safe arithmetic operations. For organizations managing large fleets of browsers, automated deployment tools should be utilized to ensure rapid patch distribution across all endpoints. Additionally, security teams can implement Content Security Policy (CSP) headers to restrict inline scripts and limit data exfiltration vectors, although this does not fix the underlying vulnerability. Monitoring browser telemetry for unusual network requests originating from renderer processes may also help detect active exploitation attempts in real-time before significant damage occurs.
This incident aligns with Common Weakness Enumeration identifier CWE-190, which describes integer overflow or wraparound when performing arithmetic operations on signed integers that leads to unexpected results and potential security vulnerabilities. Furthermore, the attack vector corresponds to ATT&CK technique T1537, specifically under the sub-category of Data Transfer from Cloud Storage via Web Service if cloud-based resources are involved, but more accurately maps to general cross-origin data theft mechanisms often associated with browser exploitation kits. The remediation emphasizes the importance of rigorous code review for memory management functions in high-performance rendering engines and continuous integration testing that includes fuzzing tests targeting arithmetic operations in layout and compositing modules.