Published: June 2024
Severity: High
Component: V8 JavaScript engine
Affected: Google Chrome versions prior to 123..6312.58
Reference: Chromium Issue 332236257
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What is CVE-2024-2625?

CVE-2024-2625 uncovers a major security flaw in Google Chrome’s V8 JavaScript engine, allowing remote attackers to potentially corrupt objects via a specially crafted HTML page. This vulnerability is rooted in the mishandling of object lifecycles—a situation where an object’s memory may be freed or reused improperly, but references to it linger, causing what is known as a "use-after-free" or a "dangling pointer" scenario.

In simple terms, a web page could trick your browser into using an object that should no longer exist. By manipulating the lifecycle of JavaScript objects, an attacker may get Chrome to read or write memory that’s meant to be off-limits, which might let them run code on your computer or steal sensitive information.

How Does This Vulnerability Work?

At the heart of this issue is the way V8 manages JavaScript objects in memory. When an object is no longer needed, it should be safely deleted. If Chrome mistakenly keeps a reference to the now-deleted object and later tries to access it, it can end up using memory that might have changed or been reallocated. Attackers can create situations where they control what gets put into this freed memory, opening the way for exploits like arbitrary code execution.

This problem is especially dangerous if exploited by loading a malicious HTML page — no user interaction needed other than visiting a website.

Proof-of-Concept (PoC) Exploit

Here’s a simplified (educational) JavaScript snippet inspired by public V8 lifecycle exploits. This doesn’t directly weaponize the bug, but helps explain the type of bug Chrome patched.

let victimArray = [1.1, 2.2, 3.3, 4.4];

function trigger() {
    let container = {obj: victimArray};
    // The function below may cause V8 to optimize and confuse object lifecycles.
    function confusion(o) {
        victimArray = null; // Force V8 to think victimArray can be garbage-collected.
        return o.obj;
    }
    // Try to get reference to an object that might be cleaned up
    let maybeDangling = confusion(container);
    // Here, 'maybeDangling' could be a highlight of a use-after-free, depending on V8’s GC timing.
    // In the real exploit, additional primitives would turn this into a memory read/write.
}

for (let i = ; i < 10000; ++i) {
    trigger();
}

NOTE: The actual bug triggered deeper V8 internals and required careful heap grooming and timing. For a real exploit, an attacker would usually use typed arrays or ArrayBuffers to achieve arbitrary read/write capabilities once they get a dangling pointer.

Heap Spraying: They fill memory with objects of their choice to shape the heap.

3. Trigger Garbage Collection: The exploit forces V8 to clear out certain objects, making a reference point to freed memory.
4. Hijack Memory: By allocating new objects (like TypedArrays or DataViews), the attacker can control what memory replaces the old object.
5. Arbitrary Read/Write: Once the V8 interpreter is confused, the exploit can read and write memory beyond the intended sandbox, potentially executing arbitrary code.

Here’s a simplified version of what step 4 might look like with more intentional spraying (high-level):

// ATTENTION: Simplified for illustration; effective exploitation requires deeper V8 know-how.
let corruption;
function sprayHeap() {
    let arr = new Array(100);
    for (let i = ; i < arr.length; i++) {
        arr[i] = new Uint32Array(100);
    }
    corruption = arr;
}
// sprayHeap would be called at the right time after confusion is triggered,
// populating the freed spot with controlled data.

Who Is at Risk and What To Do

Impacted:

Any browser based on Chromium that hasn’t patched V8 to at least this version

Attack Vector:

Fix:

References & Further Reading

- Chromium Issue Tracker: 332236257 (Restricted details)
- Chrome Releases: Stable Channel Update for Desktop (123..6312.58)
- Understand V8 Object Lifecycle (Google Blog)

Final Thoughts

Object lifecycle bugs in JavaScript engines like V8 tend to be highly prized by attackers, as they often lead to remote code execution or sandbox escapes — meaning a single bug could let someone run programs on your device just by you visiting a webpage.

If you haven’t updated Chrome in a while, do it right now. These browser security bugs can be exploited quietly and quickly by attackers in the real world.

Stay safe, and keep your browsers updated!

Disclaimer:
This article is for educational and awareness purposes only. Do not use these details for unauthorized testing or exploitation. Always act within the law and with permission.

Timeline

Published on: 03/20/2024 17:15:07 UTC
Last modified on: 04/01/2024 15:32:17 UTC