OpenSSL Security Advisory, 3rd May 2016: Patch, Patch ASAP!

Security Advisory for OpenSSL: fixed two high severity vulnerability.


Memory corruption in the ASN.1 encoder (CVE-2016-2108)

This issue affected versions of OpenSSL prior to April 2015. The bug causing the vulnerability was fixed on April 18th 2015, and released as part of the June 11th 2015 security releases.

The security impact of the bug was not known at the time.

In previous versions of OpenSSL, ASN.1 encoding the value zero represented as a negative integer can cause a buffer underflow with an out-of-bounds write in i2c_ASN1_INTEGER.

The ASN.1 parser does not normally create “negative zeroes” when parsing ASN.1 input, and therefore, an attacker cannot trigger this bug.

Padding oracle in AES-NI CBC MAC check (CVE-2016-2107)

A MITM attacker can use a padding oracle attack to decrypt traffic when the connection uses an AES CBC cipher and the server support AES-NI.

This issue was introduced as part of the fix for Lucky 13 padding attack (CVE-2013-0169).

The padding check was rewritten to be in constant time by making sure that always the same bytes are read and compared against either the MAC or padding bytes.

But it no longer checked that there was enough data to have both the MAC and padding bytes.

  • OpenSSL 1.0.2 users should upgrade to 1.0.2h
  • OpenSSL 1.0.1 users should upgrade to 1.0.1t

This issue was reported to OpenSSL on 13th of April 2016 by Juraj Somorovsky using TLS-Attacker. The fix was developed by Kurt Roeckx of the OpenSSL development team.


Patch! Patch! Patch! :-)

Published: May 03 2016