In this post, we dive into CVE-2022-32610, a critical vulnerability found in the VCU component on some MediaTek devices. This bug can let attackers achieve local privilege escalation by exploiting a race condition that leads to use-after-free. We’ll show you how it works, link to public references, and explain how you can protect your system.

What is VCU and Why is CVE-2022-32610 Dangerous?

VCU stands for Video Codec Unit. It’s often a kernel module or hardware driver used on smartphones powered by MediaTek chipsets, primarily for video encoding and decoding.

CVE-2022-32610 describes a use-after-free (UAF) scenario in the VCU, rooted in a race condition. If exploited, a less-privileged user could run code with system execution privileges, which basically means full control over the device. Exploitation doesn’t require user interaction, so malware and malicious apps could target this without asking for permission or tricking the user.

Technical Details: How the Bug Happens

The vulnerability occurs during VCU resource management. In simple terms, two or more threads can race when freeing and using memory in VCU, ending up using memory that’s already been freed.

The resource is now pointing to memory that’s already freed (a "dangling pointer").

4. A crafty user can exploit this to inject malicious data/execution.

Pseudo-code Snippet Illustrating the UAF

// Simplified skeleton of the problematic code
struct vcu_buf {
    void *data;
    bool in_use;
};

// Frees the resource
void free_vcu_buf(struct vcu_buf *buf) {
    kfree(buf->data);
    buf->data = NULL;
    buf->in_use = false;
}

// Another thread tries to use the resource
void use_vcu_buf(struct vcu_buf *buf) {
    if (buf->in_use && buf->data) {
        // Use-after-free: buf->data may now be invalid!
        process(buf->data);
    }
}

// Race condition: Both functions called in parallel

If an attacker can cause these threads to interleave just right, they can exploit the UAF to overwrite critical pointers or inject code.

The vulnerable code then executes attacker-controlled data as code or escalates privileges.

No user interaction is needed—once the malicious app is running, the attacker controls the process.

Issue ID: ALPS07203476

Original advisory:  
- MediaTek Security Bulletin June 2022
- CVE-2022-32610 on NVD

Researcher report:  
- MITRE CVE page for CVE-2022-32610

Patch and Mitigation

The fix (Patch ID: ALPS07203476) makes sure resource usage and freeing are properly locked, removing the race condition. Please check with your device vendor or SoC provider for an updated firmware containing the patch.

Review MediaTek’s public kernel sources for the VCU patch if you’re building custom ROMs.

- Use futex_wait/locking primitives around all resource free/use calls to avoid data races.

Summary

CVE-2022-32610 is a critical local privilege escalation bug due to a use-after-free in VCU. Attackers need only to execute code with regular user privileges; no user interaction is needed. Patch your device/software today with ALPS07203476.

> Always stay up to date and be careful with the apps you install!


References:  
- MediaTek Security Bulletin June 2022  
- NVD Entry for CVE-2022-32610  
- MITRE CVE Page

Timeline

Published on: 11/08/2022 21:15:00 UTC
Last modified on: 11/10/2022 13:42:00 UTC