GhostLock — CVE-2026-43499 on Samsung Galaxy A17

Full user-to-root exploit chain for CVE-2026-43499 ("GhostLock") on the Samsung Galaxy A17 SM-A175F, running Android 16 / GKI 6.12.

The chain starts from the public GhostLock primitives and ends with a usermode helper executing as:

uid=0(root) gid=0(root) groups=0(root)
context=u:r:kernel:s0

It also starts a persistent per-boot root shell through g4d / g4sh and exits without a kernel panic.

📖 Full technical write-up:
https://www.mobilehackinglab.com/blog/cve-2026-43499-ghostlock-a17-root-shell

Research note

We did not discover CVE-2026-43499. Credit for the original vulnerability and IonStack research goes to Nebula Security.

This repository documents our independent port to the Samsung Galaxy A17, the changes required for Samsung's kernel protections, and a new final exploitation stage.

For authorized security research and educational purposes only.

Target

What makes this port different?

The original ghostlock research provides the entry primitives:

pselect reclaim
      ↓
fake rt_mutex_waiter
      ↓
constrained rb-tree pointer write

On the Galaxy A17, however, the standard credential-patching endgame does not work.

Samsung KDP blocks the usual cred write

KDP protects credential-related kernel data at EL2.

On this build, attempts to modify task credentials were silently dropped even when the target addresses were correct.

So instead of writing root credentials, this port makes the kernel execute with existing privileged credentials.

New endgame: forged workqueue execution

The final stage:

constrained kernel write
        ↓
physical read/write channel
        ↓
KASLR slide recovery
        ↓
discover system_wq / cpu_pwq
        ↓
forge work_struct
        ↓
call_usermodehelper_exec_work
        ↓
/system/bin/sh
        ↓
uid=0(root), u:r:kernel:s0

A forged work item is placed on a bound system_wq pool and triggered with a ptmx allocation/free storm.

The resulting usermode helper executes with init credentials.

No task credential overwrite is required.

Exploit chain

userspace shell (uid 2000)
        │
        ▼
pselect / PI-futex primitive
        │
        ▼
constrained aligned kernel pointer write
        │
        ▼
forged pipe_buffer channel
        │
        ▼
arbitrary physical read/write
        │
        ├── recover KASLR slide
        │
        ├── locate system_wq / cpu_pwq
        │
        └── prepare forged work_struct
        │
        ▼
queue usermode-helper work
        │
        ▼
ptmx storm wakes worker
        │
        ▼
/system/bin/sh runs with init creds
        │
        ▼
uid=0(root)
        │
        ▼
g4d → @ghostlockd → g4sh

Key engineering changes

Compared with the public OnePlus port, most stages after the initial write primitive were reworked.

1. New KDP-compatible root stage

The credential-patching endgame was replaced with a forged workqueue item targeting the usermode-helper execution path.

This avoids writing protected cred structures entirely.

2. New KASLR slide oracle

The previous perf-event anchoring approach was unreliable on this device.

Instead, the exploit uses three slid pointers from the boot_id ctl_table entry:

procname
data
proc_handler

All three are cross-validated before accepting the slide.

3. Runtime workqueue discovery

cpu_pwq is discovered by walking:

system_wq → pwqs

rather than relying on a fixed device-specific offset.

4. Clean exploit exit

The original channel leaves collateral changes to struct page state that can trigger PANIC_ON_OOPS during teardown.

The current chain avoids the teardown crash and has been demonstrated exiting cleanly after root.

5. Root shell

The usermode helper starts:

g4d

which listens on the abstract Unix socket:

@ghostlockd

g4sh connects to it and provides either an interactive root shell or one-shot command execution.

/data/local/tmp/a/g4sh
/data/local/tmp/a/g4sh -c "id"

Why the Galaxy A17 is interesting

This target combines several protections that break common Android kernel exploitation techniques:

• Samsung KDP — protects credential-related kernel data at EL2
• DEFEX — restricts privileged execution from untrusted paths
• SELinux
• PANIC_ON_OOPS / PANIC_ON_BUG
• Large arm64 KASLR slides
• Pointer-only constrained write primitive

This forced a different exploit strategy from the usual:

arbitrary RW → patch cred → disable SELinux

Instead:

arbitrary RW → recover runtime state → forge kernel work → execute usermode helper

Build

Requires a recent Android NDK.

make        # BZA5 firmware (kernel 6.12.23)
make czg1   # CZG1 firmware (kernel 6.12.38): per-target slide anchors,
            # offsets are uname-keyed at runtime

Produces:

ghostlock   # exploit (ghostlock-czg1 for the CZG1 build)
g4d         # static root-shell daemon
g4sh        # root-shell client

Run

Push the binaries:

adb push ghostlock /data/local/tmp/a/g4
adb push g4d /data/local/tmp/a/g4d
adb push g4sh /data/local/tmp/a/g4sh

adb shell 'chmod 755 /data/local/tmp/a/g4 /data/local/tmp/a/g4d /data/local/tmp/a/g4sh'

Run the reboot-aware exploit loop:

./scripts/rr_loop4.sh

After ROOTED:

adb shell /data/local/tmp/a/g4sh

Or execute a single command:

adb shell '/data/local/tmp/a/g4sh -c "id"'

Expected result:

uid=0(root) gid=0(root) groups=0(root) context=u:r:kernel:s0

Reliability

The primitive is probabilistic and strongly dependent on boot conditions.

Successful exploitation may require repeated attempts. The included rr_loop4.sh script handles retries and reboot cycles automatically.

This is a research exploit, not an instant one-shot rooting tool.

QEMU validation

qemu-e2e/ contains an end-to-end validation harness using the extracted Samsung kernel.

The harness was used to test:

• exploit-chain changes
• KASLR handling
• workqueue forging
• usermode-helper execution
• clean exploit teardown
• g4d / g4sh round trips

The Samsung kernel image itself is not included.

See:

qemu-e2e/

for setup instructions.

Repository layout

Makefile
src/                  exploit source and device profiles
src/daemon/           g4d root daemon + g4sh client
docs/OFFSETS.md       validated device offsets
docs/PORTING.md       porting notes
examples/             proof-of-root artifacts
scripts/rr_loop4.sh   reboot-aware exploit loop
qemu-e2e/             end-to-end QEMU validation

Related research

Original GhostLock / IonStack research

NebuSec:

https://nebusec.ai/research/ionstack-part-3/

https://github.com/NebuSec/CyberMeowfia/tree/main/IonStack

OnePlus port

https://github.com/JoinChang/ghostlock-oneplus

Mobile Hacking Lab write-up

A deeper look at the Samsung Galaxy A17 port, KDP limitations, KASLR recovery, workqueue-based final stage, and root-shell implementation:

https://www.mobilehackinglab.com/blog/cve-2026-43499-ghostlock-a17-root-shell

Proof of root

Real-device artifacts are available under:

examples/

including exploit logs and root-context verification.

Example:

uid=0(root)
gid=0(root)
groups=0(root)
context=u:r:kernel:s0

Disclaimer

This proof of concept is provided for educational and authorized security research purposes only.

Only use it on devices and environments you own or have explicit permission to test.