cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. In affected versions Cipher.updateinto would accept Python objects which implement the buffer protocol, but provide only immutable buffers. This would allow immutable objects (such as bytes) to be mutated, thus violating fundamental rules of Python and resulting in corrupted output. This now correctly raises an exception. This issue has been present since updateinto was originally introduced in cryptography 1.8.

Python Cryptographic Authority cryptography could provide weaker than expected security, caused by an encoding mismatch regarding critical options with OpenSSH. An attacker could exploit this vulnerability to launch further attacks on the system

Summary

Calling loadpempkcs7certificates or loadderpkcs7certificates 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 loadderpkcs7certificates, loadpempkcs7certificates

pemp7 = b""" -----BEGIN PKCS7----- MAsGCSqGSIb3DQEHAg== -----END PKCS7----- """

derp7 = b"\x30\x0B\x06\x09\x2A\x86\x48\x86\xF7\x0D\x01\x07\x02"

loadpempkcs7certificates(pemp7) loadderpkcs7certificates(derp7)

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.

A buffer-overflow flaw was found in the python-cryptography package. In certain sequences of update() calls when symmetrically encrypting very large payloads (>2GB) could result in an integer overflow, leading to buffer overflows. Note: This fix is a workaround for the OpenSSL CVE-2021-23840 flaw. Source: pyca/cryptography project