CVE-2022-32608 - JPEG Race Condition in Android Leads to Local Privilege Escalation (With Code, Exploit, and Patch Overview)

In 2022, a serious security issue tracked as CVE-2022-32608 was discovered in Android's JPEG library. Due to a race condition—where two parts of a program access shared data at the same time and at least one writes to it—this bug can be exploited to perform a use-after-free (UAF) attack. The end result? A malicious local app could gain higher privileges (even 'System' level) without any user interaction.

Let's dive into the vulnerability, see how it works (with code), how it can be exploited, and where you can find the patch.

Component: JPEG handling, likely from libjpeg or similar in Android's system libraries.

- Impact: Local escalation of privileges. If exploited, an attacker becomes 'System', much higher than a normal app user.
- Access Required: Local — attacker needs code execution on the device. No user interaction is needed.
- Patch: ALPS07388753 (MediaTek security bulletin also references ID: ALPS07388753)
- Reference: Android Security Bulletin October 2022

Root Cause

When a JPEG image is being processed, certain libraries manage memory allocations for processing buffers. In this bug, a pointer to memory may be used _after_ it was freed—if two actions overlap incorrectly:

Thread A is freeing or resetting a JPEG structure.

2. Thread B is compressing/decompressing, referencing that same structure without proper locking.

This is generally what is known as a classic race condition.

Suppose you have this kind of simplified scenario

typedef struct {
    unsigned char* buffer;
    size_t bufsize;
    // ... other members
} jpeg_context;

void process_jpeg(jpeg_context* ctx) {
    // (A) Use the buffer for some operation
    memcpy(temp, ctx->buffer, ctx->bufsize);
    // ... do stuff with temp
}

void free_jpeg(jpeg_context* ctx) {
    free(ctx->buffer); // Memory gets freed
    ctx->buffer = NULL;
}

If two threads do this

// Thread 1:
process_jpeg(ctx);    // Tries to use ctx->buffer

// Thread 2:
free_jpeg(ctx);       // Frees ctx->buffer

Without any locks, it's possible for process_jpeg to use a pointer that's already been freed, causing use-after-free.

Demonstrating the Race (Pseudo-Exploit)

While public PoC is often not available for fresh Android bugs, here's a simplified workflow that emulates what an exploit could look like:

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

typedef struct {
    unsigned char* buffer;
    size_t bufsize;
} jpeg_context;

jpeg_context* ctx;

void* thread_func1(void* arg) {
    // Simulate processing that uses freed memory
    for (int i = ; i < 100000; ++i) {
        if (ctx->buffer) {
            memcpy((void*)malloc(ctx->bufsize), ctx->buffer, ctx->bufsize);
        }
    }
    return NULL;
}

void* thread_func2(void* arg) {
    // Simulate freeing in the middle of processing
    for (int i = ; i < 100000; ++i) {
        if (ctx->buffer) {
            free(ctx->buffer);
            ctx->buffer = NULL;
        }
    }
    return NULL;
}

int main() {
    ctx = malloc(sizeof(jpeg_context));
    ctx->bufsize = 4096;
    ctx->buffer = malloc(ctx->bufsize);

    pthread_t t1, t2;
    pthread_create(&t1, NULL, thread_func1, NULL);
    pthread_create(&t2, NULL, thread_func2, NULL);

    pthread_join(t1, NULL);
    pthread_join(t2, NULL);

    free(ctx);
    return ;
}

NOTE: On Android, in actual exploitation, the attacker would take advantage of system libraries running in privileged context (like the 'System' service). By racing allocation and freeing, the attacker may get the system to write data to freed memory, potentially hijacking control flow.

Exploitation Impact

- No User Involvement: The user does NOT need to open a malicious JPEG, click anything, or approve any permissions.

Attack Vector: Malicious app running locally can trigger this race.

- Result: Attacker process becomes 'System' (very powerful: can bypass many Android security boundaries).

Android Security Bulletin Reference:

https://source.android.com/security/bulletin/2022-10-01#2022-10-01-security-patch-level-vulnerability-details

Patch Description (Simplified)

- Proper mutex/lock mechanisms added.

What Should You Do?

- Patch Now: Make sure your device is up to date with the October 2022 (or newer) Android security patch level.

Summary

CVE-2022-32608 shows how a bug in a JPEG handler can grant "god mode" to any local malicious app, all due to a small mistake with how memory is used and shared. If you manage devices or work with Android source code, make sure you have the fix for ALPS07388753. And as always, keep your device's software up to date!

Timeline

Published on: 11/08/2022 21:15:00 UTC
Last modified on: 11/10/2022 13:53:00 UTC