CVE-2020-25659

Advisory

Cryptography 3.2 and prior are vulnerable to Bleichenbacher timing attacks in the RSA decryption API, via timed processing of valid PKCS#1 v1.5 ciphertext.

Affected package

Affected versions

Fixed versions

Vulnerability changelog

~~~~~~~~~~~~~~~~

* **SECURITY ISSUE:** Attempted to make RSA PKCS1v1.5 decryption more constant
time, to protect against Bleichenbacher vulnerabilities. Due to limitations
imposed by our API, we cannot completely mitigate this vulnerability and a
future release will contain a new API which is designed to be resilient to
these for contexts where it is required. Credit to **Hubert Kario** for
reporting the issue. *CVE-2020-25659*
* Support for OpenSSL 1.0.2 has been removed. Users on older version of OpenSSL
will need to upgrade.
* Added basic support for PKCS7 signing (including SMIME) via
:class:`~cryptography.hazmat.primitives.serialization.pkcs7.PKCS7SignatureBuilder`.

.. _v3-1-1:

Resources

• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-25659
• https://github.com/pyca/cryptography/pull/5507/commits/ce1bef6f1ee06ac497ca0c837fbd1c7ef6c2472b
• https://www.oracle.com/security-alerts/cpuapr2022.html
• https://www.oracle.com/security-alerts/cpujul2022.html