CVE-2026-121033 in Chrome
Summary
by MITRE • 11/03/2026
Uninitialized resource in GPU in Google Chrome on on Android prior to 157.0.8103.38 allowed a remote attacker who had compromised the renderer process to read memory outside the sandbox 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 uninitialized resource issue within the Graphics Processing Unit subsystem of Google Chrome on Android represents a significant breach in browser isolation mechanisms. This flaw, present in versions prior to 157.0.8103.38, stems from improper initialization of memory buffers or state variables used during GPU-accelerated rendering operations. When the browser processes complex web content involving WebGL or other hardware-accelerated graphics APIs, it relies on strict boundaries between the untrusted renderer process and the more privileged sandboxed environment. The failure to properly initialize these resources creates a window where undefined data remains in memory rather than being cleared or set to safe defaults. This oversight allows for potential information disclosure if an attacker can trigger specific rendering paths that expose this uninitialized state back to the application logic.
From a technical perspective, the core of the issue lies in how Chrome manages shared memory between the renderer process and the GPU service. In modern browsers, the renderer runs with limited privileges to contain damage from malicious web content. However, when interacting with hardware acceleration features, certain data structures are passed across these trust boundaries. If a resource such as a texture buffer, shader program state, or command queue entry is allocated but not fully initialized before being used in a context where its contents might be read back by the renderer process, it can leak sensitive information from adjacent memory regions. This includes potentially stack variables, heap metadata, or even data belonging to other processes if shared memory mappings are involved improperly. The severity of this flaw is classified as medium because while it does not allow direct code execution on the host system, it facilitates a sandbox escape that compromises confidentiality guarantees essential for web security.
The operational impact of this vulnerability centers on unauthorized memory access by an attacker who has already achieved renderer process compromise. In typical attack scenarios, such compromise might result from exploiting another lower-severity bug in JavaScript or HTML parsing to execute arbitrary code within the browser's isolated environment. Once inside the renderer, a malicious actor could craft a specially designed HTML page that triggers the uninitialized resource condition during GPU operations. By carefully manipulating input parameters and timing of graphics commands, the attacker can cause the system to read memory locations outside the intended sandbox boundaries. This capability enables the exfiltration of sensitive data such as cookies, session tokens, or other credentials stored in browser memory, effectively breaking the fundamental security model that protects users from malicious websites.
This vulnerability aligns with CWE-457, which describes the use of an uninitialized variable, and falls under the broader category of improper resource initialization often seen in complex software systems involving hardware interaction. In terms of threat modeling and adversary tactics, this exploit path corresponds to ATT&CK technique T1059, specifically command-line or script execution within a sandboxed environment leading to lateral movement or data staging. The ability to read outside the sandbox is particularly dangerous as it undermines the principle of least privilege enforced by modern browsers. Defenders should note that while the initial entry point requires renderer compromise, the subsequent memory access capability significantly elevates the risk profile from an isolated script execution to a potential full browser context takeover depending on what data resides in the accessible memory regions.
Mitigation strategies primarily involve applying the vendor-provided patch available in Google Chrome version 157.0.8103.38 and later for Android devices. Organizations relying on enterprise deployments of Chromium-based browsers must ensure automatic update policies are enforced to minimize exposure windows. For developers integrating custom rendering engines or modifying browser source code, rigorous static analysis tools should be employed to detect uninitialized variable usage in GPU-related modules. Additionally, implementing stricter bounds checking during memory allocation and ensuring all buffers are zeroed out before being exposed across trust boundaries can prevent similar issues. Security teams should also monitor for anomalous behavior indicative of sandbox escapes, such as unexpected network connections initiated by browser processes or unusual memory access patterns detected through endpoint detection systems.