CVE-2026-11645: Out-of-Bounds Memory Access in Google Chrome V8 Engine

The Google Chrome V8 engine is responsible for executing JavaScript and WebAssembly code within the browser. To maintain high performance, V8 compiles source code directly into native machine code using a multi-tiered execution pipeline. This pipeline includes the Ignition interpreter, Sparkplug non-optimizing compiler, Maglev mid-tier compiler, and the TurboFan high-tier optimizing compiler.

During high-tier compilation, TurboFan performs sophisticated optimizations such as type specialization, loop induction variable analysis, and redundant bounds-check elimination. If an optimization step contains mathematical or logical errors, the compiler may discard essential runtime safety checks.

CVE-2026-11645 represents a critical flaw within this optimization process. An attacker can leverage this flaw to trigger an out-of-bounds read (CWE-125) and write (CWE-787) inside the memory heap allocated to the execution thread, allowing unauthorized state manipulation and memory access.

The root cause of CVE-2026-11645 lies in TurboFan's range analysis phase, which tracks the possible minimum and maximum values of loop induction variables and array indices. When the compiler evaluates an array access instruction like array[index], it evaluates the known range of index against the static size of the array. If the compiler determines that index is guaranteed to be within safe bounds, it optimizes away the runtime bounds check to reduce execution overhead.

In this vulnerability, a logic flaw in the range tracker incorrectly computes the maximum possible value of a variable modified within a loop or through specific bitwise operations. This miscalculation leads TurboFan to believe that the variable cannot exceed the array boundary, when in fact it can. At runtime, the compiled native code executes without verifying the index, enabling access to memory locations outside the allocated backing store.

Alternatively, this behavior can be triggered when an optimized code path assumes an array remains in a specific 'ElementsKind' state, but an unexpected state transition occurs. If the array is mutated to a different layout, the compiled code reads or writes using stale size and offset assumptions, resulting in memory corruption.

In V8, range representation and bounds-check elimination are performed in the representation selection and optimization phases of the compiler graph. The compiler tracks ranges using a specialized structure that maintains lower and upper limits. A simplified conceptual logic of the vulnerable range calculation can be represented as follows:

// Conceptual vulnerable optimization logic in range-analysis.cc
class Range {
public:
    int32_t min_value;
    int32_t max_value;
 
    // Vulnerable range union calculation
    void UnionWith(const Range& other) {
        this->min_value = std::min(this->min_value, other.min_value);
        // BUG: Incomplete check for integer overflow on upper bounds optimization
        this->max_value = std::max(this->max_value, other.max_value);
    }
};

The fix introduces strict validation of integer bounds during range union and intersection steps. It prevents the optimizer from discarding bounds checks unless the safety criteria are met under all possible execution paths:

// Conceptual patched logic enforcing safe range checking
void UnionWith(const Range& other) {
    this->min_value = std::min(this->min_value, other.min_value);
    // PATCH: Explicit safety margin check and integer overflow validation
    if (SafeAddition(this->max_value, other.max_value)) {
        this->max_value = std::max(this->max_value, other.max_value);
    } else {
        this->MarkAsUnbounded(); // Force bounds checks to be retained
    }
}

Exploitation of CVE-2026-11645 requires a multi-stage approach to bypass modern browser mitigations, primarily the V8 Heap Sandbox. Since V8 confines its pointers within a 4GB virtual address space on 64-bit platforms, direct arbitrary write to system memory is prevented. Instead, attackers construct complex read/write primitives within this sandbox boundary.

The exploit sequence begins by defining an array and optimizing a function that indexes into it. By passing a crafted input that violates the range optimizer's assumptions, the exploit gains an initial out-of-bounds read and write. The read is utilized to locate adjacent JS objects and leak their internal 'Map' pointers. This bypasses pointer compression protections and allows the attacker to learn the layout of the V8 heap.

Next, the write capability is leveraged to corrupt the length field or the elements backing store of an adjacent JSArray or ArrayBuffer. By setting the length to 0xFFFFFFFF, the attacker achieves an unrestricted read/write primitive within the 4GB sandbox. Finally, the attacker overwrites JIT-compiled function code or WASM execution buffers to execute arbitrary shellcode within the context of the sandboxed utility process.

The security impact of CVE-2026-11645 is classified as High, with a CVSS v3.1 base score of 8.8. An unauthenticated remote attacker can execute arbitrary code inside the Google Chrome renderer process simply by convincing a target user to load a malicious webpage. No complex administrative privileges or system-level access are required.

Because the V8 engine operates inside Chromium's multi-process sandbox, shellcode execution is restricted to the privileges of the renderer. An attacker cannot directly access the underlying operating system files, install system-wide malware, or execute administrative tasks using this vulnerability alone.

To achieve full system compromise, this exploit must be chained with a secondary vulnerability, such as an operating system kernel flaw or a browser IPC (Inter-Process Communication) broker vulnerability. However, control of the renderer process still allows the attacker to steal sensitive session data, read cookies, intercept active user transactions, and capture input on currently open tabs.

Defending against CVE-2026-11645 requires a combination of timely patching and proactive system monitoring. The most critical defense is ensuring all instances of Google Chrome are upgraded to version 149.0.7827.103 or later on Windows and macOS, and version 149.0.7827.102 or later on Linux systems.

At the host level, Endpoint Detection and Response (EDR) agents should be configured to flag anomalous process creations stemming from browser binaries. Because renderer helper processes should never execute system command interpreters, any launch of programs like /bin/bash or cmd.exe by Chrome indicates a sandbox escape attempt.

# Conceptual Snort rule targeting standard obfuscated array allocation patterns
alert tcp any any -> any any (msg:"INDICATOR-OBFUSCATION V8 JIT Array Spraying Attempt"; flow:established,to_client; content:"new Array"; content:"for"; pcre:"/\b\w+\[\w+\]\s*=\s*0x[0-9a-fA-F]{8}/"; sid:1000001; rev:1;)

Additionally, implementing Application Guard or running the browser in isolated container environments can restrict physical device access, minimizing the risk of a successful sandbox escape chain.