CVE-2022-26765 refers to a severe race condition flaw found in Apple operating systems affecting multiple platforms, such as watchOS, tvOS, macOS Monterey, iOS, and iPadOS. The vulnerability was assigned by Apple as part of their continual security improvement. Apple patched this issue in watchOS 8.6, tvOS 15.5, macOS Monterey 12.4, iOS 15.5, and iPadOS 15.5.

This bug was particularly dangerous because a clever attacker with read and write rights from a userland process could exploit it to bypass Pointer Authentication (PAC). That means a critical layer of executable code integrity, which is designed to prevent exploitation of memory corruption bugs, could be sidestepped.

Official Apple Advisory:
https://support.apple.com/en-us/HT213252

What Is Pointer Authentication?

Pointer Authentication, used in Apple’s A-series chips (starting from A12), uses cryptographic signatures (Pointer Authentication Codes or PACs) to stop attackers from forging pointers and taking control of code execution through classic memory corruption exploits.

What Was the Problem?

A race condition in Apple’s OS code meant that “state handling” was not always reliable under concurrent access. An attacker who could read and write memory could trigger this race, causing the system to process an outdated or incorrect state—potentially getting around the PAC checks entirely.

Apple Site Note

> "A race condition was addressed with improved state handling. This issue is fixed ... A malicious application with arbitrary read and write capability may be able to bypass Pointer Authentication."

Let’s break down a likely attack chain

1. Arbitrary Read/Write: Attacker first gains read/write privileges (often through prior memory corruption or sandbox escape).
2. Race Setup: The attacker orchestrates threads/processes to simultaneously access and change some pointer-keeping objects.
3. Bypassing PAC: If timed perfectly, the attack leverages the race that happens *before* PAC checks are strictly enforced, loading unverified, attacker-controlled pointers.

This means any further PAC-enforced code protections can be bypassed, opening the door to privilege escalation or code execution attacks.

Example Code Snippet

Here’s a simplified conceptual code demonstrating how a race might cause trouble if state is not managed atomically:

// Hypothetical vulnerable system code (simplified for illustration)
typedef struct {
    void (*function_ptr)(void);
    uint64_t pac_signature;
} SecuredPtr;

SecuredPtr global_ptr;

// Thread 1 (Attacker): Overwrites SecuredPtr while Thread 2 uses it
void *thread_race_overwrite(void *arg) {
    // Sleep to increase likelihood of race triggering
    sleep(1); 
    // Overwrite both function pointer and PAC at the same time
    global_ptr.function_ptr = attacker_function;
    global_ptr.pac_signature = generate_attacker_signature();
    return NULL;
}

// Thread 2: System code validates before using the pointer
void use_secured_pointer() {
    if (check_pac(global_ptr.function_ptr, global_ptr.pac_signature)) {
        global_ptr.function_ptr();
    } else {
        printf("BAD PAC\n");
    }
}

If global_ptr is not protected with a mutex or atomic swap, the attacker can win the race—changing both pointer and PAC right between validation and use.


## Proof-of-Concept Pseudocode (for Research/Education)

Below is a pseudocode for exploit illustrating race window exploitation

# DO NOT USE THIS FOR MALICIOUS PURPOSES

shared_pac_pointer = (safe_function, safe_pac)

def attacker():
    sleep(.01)
    # Race to overwrite pointer and PAC
    shared_pac_pointer = (attacker_func, forged_pac)

def victim():
    if check_pac(shared_pac_pointer):
        execute(shared_pac_pointer.func)
    else:
        print("PAC error")

# Run threads in parallel to exploit race

How Was It Fixed?

Apple improved state handling by properly synchronizing accesses or making critical memory sections atomic and impossible to race. They also likely reviewed their PAC validation code to make sure no old or untrusted state can sneak in during a race window.

macOS Monterey 12.3 and earlier

- iOS/iPadOS 15.4.1 and earlier

tvOS 15.4.1 and earlier

Update as soon as possible if you’re on any affected version.

References and More Reading

- Apple Security Updates (HT213252)
- Apple Platform Security - Pointer Authentication
- Example similar race condition writeup: Project Zero - Exploiting race conditions on iOS

TL;DR

CVE-2022-26765 was a nasty bug in Apple OS’s pointer authentication logic—a race condition that let attackers bypass core security checks if they got user application memory access. It’s fixed in the latest updates, and is a reminder that even advanced security tech like PAC can be undermined by race bugs and improper state handling.

Timeline

Published on: 05/26/2022 20:15:00 UTC
Last modified on: 06/08/2022 14:19:00 UTC