cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. Prior to 46.0.5, the public_key_from_numbers (or EllipticCurvePublicNumbers.public_key()), EllipticCurvePublicNumbers.public_key(), load_der_public_key() and load_pem_public_key() functions do not verify that the point belongs to the expected prime-order subgroup of the curve. This missing validation allows an attacker to provide a public key point P from a small-order subgroup. This can lead to security issues in various situations, such as the most commonly used signature verification (ECDSA) and shared key negotiation (ECDH). When the victim computes the shared secret as S = [victim_private_key]P via ECDH, this leaks information about victim_private_key mod (small_subgroup_order). For curves with cofactor > 1, this reveals the least significant bits of the private key. When these weak public keys are used in ECDSA , it's easy to forge signatures on the small subgroup. Only SECT curves are impacted by this. This vulnerability is fixed in 46.0.5.

cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. Starting in version 38.0.0 and prior to version 42.0.4, if `pkcs12.serialize_key_and_certificates` is called with both a certificate whose public key did not match the provided private key and an `encryption_algorithm` with `hmac_hash` set (via `PrivateFormat.PKCS12.encryption_builder().hmac_hash(...)`, then a NULL pointer dereference would occur, crashing the Python process. This has been resolved in version 42.0.4, the first version in which a `ValueError` is properly raised.

A flaw was found in the python-cryptography package. This issue may allow a remote attacker to decrypt captured messages in TLS servers that use RSA key exchanges, which may lead to exposure of confidential or sensitive data.

cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. Calling `load_pem_pkcs7_certificates` or `load_der_pkcs7_certificates` could lead to a NULL-pointer dereference and segfault. 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. This vulnerability has been patched in version 41.0.6.

The cryptography package before 41.0.2 for Python mishandles SSH certificates that have critical options.

cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. In affected versions `Cipher.update_into` 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 `update_into` was originally introduced in cryptography 1.8.

In the cryptography package before 3.3.2 for Python, certain sequences of update calls to symmetrically encrypt multi-GB values could result in an integer overflow and buffer overflow, as demonstrated by the Fernet class.

python-cryptography 3.2 is vulnerable to Bleichenbacher timing attacks in the RSA decryption API, via timed processing of valid PKCS#1 v1.5 ciphertext.

HKDF in cryptography before 1.5.2 returns an empty byte-string if used with a length less than algorithm.digest_size.