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USN-3199-2: Python Crypto regression

17 February 2017

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



  • python-crypto - cryptographic algorithms and protocols for Python


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

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.

Update instructions

The problem can be corrected by updating your system to the following package versions:

Ubuntu 16.10
Ubuntu 16.04
Ubuntu 14.04

In general, a standard system update will make all the necessary changes.


Related notices

  • USN-3199-1: python3-crypto, python-crypto-doc, python-crypto
  • USN-3199-3: python3-crypto, python-crypto