Affected versions of Cryptography 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.

Affected versions of the cryptography package are vulnerable to Improper Input Validation due to missing prime-order subgroup validation for SECT elliptic-curve points. The public_key_from_numbers, EllipticCurvePublicNumbers.public_key(), load_der_public_key(), and load_pem_public_key() entry points accept attacker-supplied public keys without verifying that the provided point lies in the expected prime-order subgroup, enabling small-subgroup points to pass as valid.

Versions of Cryptograph starting from 35.0.0 are susceptible to a security flaw in the POLY1305 MAC algorithm on PowerPC CPUs, which allows an attacker to disrupt the application's state. This disruption might result in false calculations or cause a denial of service. The vulnerability's exploitation hinges on the attacker's ability to alter the algorithm's application and the dependency of the software on non-volatile XMM registers.
https://github.com/pyca/cryptography/commit/89d0d56fb104ac4e0e6db63d78fc22b8c53d27e9

The `cryptography` library updates its BoringSSL and OpenSSL dependencies in CI due to a security concern. Specifically, certain non-default TLS server configurations can cause unbounded memory growth when processing TLSv1.3 sessions, leading to a potential Denial of Service (DoS) attack. The issue arises when the `SSL_OP_NO_TICKET` option is used without early data support and default anti-replay protection. Under these conditions, the session cache can become misconfigured, preventing it from flushing properly and causing it to grow indefinitely. A malicious client can exploit this scenario to trigger a DoS attack, although it can also occur accidentally during normal operations. This vulnerability affects only TLS servers supporting TLSv1.3 and does not impact TLS clients. Additionally, the FIPS modules in versions 3.2, 3.1, and 3.0, as well as OpenSSL 1.0.2, are not affected by this issue.

Cryptography version 42.0.5 introduces a limit on the number of name constraint checks during X.509 path validation to prevent denial of service attacks.
https://github.com/pyca/cryptography/commit/4be53bf20cc90cbac01f5f94c5d1aecc5289ba1f

Affected versions of Cryptography have a vulnerable statically linked copy of OpenSSL included in cryptography wheels.

The `cryptography` library has updated its BoringSSL and OpenSSL dependencies in CI due to a security concern. Specifically, the issue involves the functions `EVP_PKEY_param_check()` and `EVP_PKEY_public_check()`, which are used to check DSA public keys or parameters. These functions can experience significant delays when processing excessively long DSA keys or parameters, potentially leading to a Denial of Service (DoS) if the input is from an untrusted source. The vulnerability arises because the key and parameter check functions do not limit the modulus size during checks, despite OpenSSL not allowing public keys with a modulus over 10,000 bits for signature verification. This issue affects applications that directly call these functions and the OpenSSL `pkey` and `pkeyparam` command-line applications with the `-check` option. The OpenSSL SSL/TLS implementation is not impacted, but the OpenSSL 3.0 and 3.1 FIPS providers are affected by this vulnerability.

Cryptography starting from version 42.0.0 updates its CI configurations to use newer versions of BoringSSL or OpenSSL as a countermeasure to CVE-2023-5678. This vulnerability, affecting the package, could cause Denial of Service through specific DH key generation and verification functions when given overly long parameters.

The cryptography library has updated its OpenSSL dependency in CI due to security concerns. This vulnerability arises when processing maliciously formatted PKCS12 files, which can cause OpenSSL to crash, leading to a potential Denial of Service (DoS) attack. PKCS12 files, often containing certificates and keys, may come from untrusted sources. The PKCS12 specification allows certain fields to be NULL, but OpenSSL does not correctly handle these cases, resulting in a NULL pointer dereference and subsequent crash. Applications using OpenSSL APIs, such as PKCS12_parse(), PKCS12_unpack_p7data(), PKCS12_unpack_p7encdata(), PKCS12_unpack_authsafes(), and PKCS12_newpass(), are vulnerable if they process PKCS12 files from untrusted sources. Although a similar issue in SMIME_write_PKCS7() was fixed, it is not considered significant for security as it pertains to data writing. This issue does not affect the FIPS modules in versions 3.2, 3.1, and 3.0.

cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. Starting in version 38.0.0 and before 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.

Cryptography 42.0.0 updates its bundled dependency 'OpenSSL' so to include the commit fix for CVE-2023-6237: Checking excessively long invalid RSA public keys may take a long time.