USN-3199-2: Python Crypto regression

Ubuntu Security Notice USN-3199-2

17th February, 2017

Python Crypto regression

A security issue affects these releases of Ubuntu and its
derivatives:

Ubuntu 16.10
Ubuntu 16.04 LTS
Ubuntu 14.04 LTS

Summary

USN-3199-1 introduced a regression in the Python Cryptography Toolkit which
caused programs which relied on the original behavior to fail.

Software description

python-crypto
– cryptographic algorithms and protocols for Python

Details

USN-3199-1 fixed a vulnerability in the Python Cryptography Toolkit.
Unfortunately, various programs depended on the original behavior of the Python
Cryptography Toolkit which was altered when fixing the vulnerability. This
update retains the fix for the vulnerability but issues a warning rather than
throwing an exception. Code which produces this warning should be updated
because future versions of the Python Cryptography Toolkit re-introduce the
exception.

We apologize for the inconvenience.

Original advisory details:

It was discovered that the ALGnew function in block_template.c in the Python
Cryptography Toolkit contained a heap-based buffer overflow vulnerability.
A remote attacker could use this flaw to execute arbitrary code by using
a crafted initialization vector parameter.