CVE-2026-121096 in Chrome
Summary
by MITRE • 11/03/2026
Incomplete cleanup in V8 in Google Chrome prior to 157.0.8103.38 allowed a local attacker to read memory via a local program. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified as an incomplete cleanup issue within the V8 JavaScript engine, which powers Google Chrome versions prior to 157.0.8103.38, represents a critical failure in memory management protocols during object lifecycle termination. This flaw specifically arises when the garbage collection mechanism or explicit deallocation routines fail to properly nullify references or release associated resources after an object is no longer required by the application logic. In complex web applications where dynamic content and asynchronous operations are prevalent, such lapses can leave dangling pointers or retain access to memory regions that should have been marked as free for reuse. This situation creates a window of opportunity for local attackers who possess the ability to execute arbitrary code within the browser's sandboxed environment, albeit with limited privileges compared to the host operating system.
From a technical perspective, this vulnerability aligns closely with CWE-401, which describes missing release of memory after effective usage, and potentially CWE-787, out-of-bounds write if the improper cleanup leads to heap corruption during subsequent allocations. The core issue lies in the V8 engine's internal handling of JavaScript objects that interact with native C++ components through bindings like Node-API or WebAssembly interfaces. When these interactions conclude without a rigorous reset of state variables and pointer references, residual data remains accessible in memory segments that might be reallocated to other processes or scripts running within the same renderer process. This persistence of sensitive information violates the principle of least privilege by allowing subsequent operations to inadvertently read data intended for previous contexts, thereby breaching isolation boundaries established by the browser's security model.
The operational impact of this vulnerability is primarily centered on information disclosure and potential escalation of privileges through memory corruption techniques. Although classified as medium severity in Chromium’s internal scoring system due to the requirement for local execution context, the implications are significant for users handling sensitive data within web applications. An attacker could exploit this flaw to extract cookies, session tokens, or other authentication credentials stored in JavaScript variables that were not properly cleared from memory. Furthermore, if combined with other vulnerabilities such as type confusion bugs, this incomplete cleanup could facilitate more severe attacks including arbitrary code execution by manipulating the heap structure during reallocation phases. The ability to read memory via a local program means that any malicious script injected into a webpage or executed through developer tools can leverage this flaw to probe adjacent memory spaces for valuable targets.
Mitigation strategies must focus on both immediate patching and long-term architectural improvements within the V8 engine's garbage collection subsystem. Users should immediately update Google Chrome to version 157.0.8103.38 or later, where these cleanup routines have been corrected to ensure all references are explicitly nullified and memory is properly released upon object destruction. For developers integrating custom bindings with V8, it is crucial to implement strict lifecycle management practices that verify the complete deallocation of resources before returning control to the garbage collector. Additionally, enabling Chrome’s built-in security features such as Site Isolation can help mitigate the impact by ensuring that different origins are isolated in separate processes, thereby limiting the scope of memory access even if a vulnerability is exploited. Regular auditing of JavaScript code for potential memory leaks and utilizing static analysis tools designed to detect improper resource management patterns will further reduce the risk surface associated with this class of vulnerabilities.
In terms of threat intelligence frameworks, this incident maps to MITRE ATT&CK technique T1074, specifically Data Staged or Local Data Manipulation if used in conjunction with other exploits, but more accurately reflects aspects of privilege escalation via memory corruption techniques often seen in advanced persistent threats targeting browser engines. The failure to clean up state effectively allows attackers to maintain footholds within the application’s runtime environment longer than intended, facilitating lateral movement within the local system context if sandbox escape mechanisms are subsequently bypassed. Security teams should monitor for indicators of exploitation such as unusual memory allocation patterns or spikes in CPU usage associated with garbage collection cycles, which may signal active attempts to leverage this incomplete cleanup flaw. By addressing these foundational issues in memory management and enforcing rigorous update policies, organizations can significantly reduce their exposure to browser-based attacks that rely on subtle timing windows and state inconsistencies within the V8 engine.