The conference paper linked below introduces a novel KCI attack against several TLS libraries. All TLS implementations supporting non-ephemeral (Elliptic Curve) Diffie-Hellman key exchange with fixed (Elliptic Curve) Diffie-Hellman client authentication are vulnerable to this attack, including OpenSSL v1.0.2. No other versions of OpenSSL are vulnerable. Attacker possessing a client certificate with the corresponding secret key will be able to impersonate other servers, posing as a man-in-the-middle, while being able to eavesdrop on and modify plaintext messages at will. Research paper with flaw details: https://www.usenix.org/system/files/conference/woot15/woot15-paper-hlauschek.pdf External References: https://kcitls.org/
Created openssl tracking bugs for this issue: Affects: fedora-all [bug 1252472]
Linked paper includes the following info about OpenSSL: The currently most commonly used branches of the OpenSSL library (branches 0.9.8, 1.0.0, and 1.0.1) do not support the necessary TLS options (so systems such as Google Android seem to be safe at this time). However, the source code of the OpenSSL library contains ‘TODO’s in the source code for implementing support for fixed ECDH handshakes. Not much code is missing for fixed ECDH support in OpenSSL (we added basic support with only a few lines of code for our MitM setup). After engaging the OpenSSL developer team during the responsible disclosure process, we found that the newest branch (branch 1.0.2) just recently added support for static DH, but not (yet) for fixed ECDH handshakes. That means, client that use the 1.0.2 branch of OpenSSL might as well be vulnerable to our attack. This is apparently referring to: https://git.openssl.org/?p=openssl.git;a=commitdiff;h=0ffa49970b9f8ea66b43ce2eb7f8fd523b65bc2c https://git.openssl.org/?p=openssl.git;a=commitdiff;h=c523eb98d1694afd5d73cb5fe3b521c6064c130f
OpenSSL 1.0.1u, 1.0.2i, and 1.1.0a address KCI issue for GOST cipher suites: https://git.openssl.org/?p=openssl.git;a=commitdiff;h=ab650f07a0dabc01a4410f8f702c3cea7932da62 GOST support is not enabled in OpenSSL packages in Red Hat Enterprise Linux.
This CVE Bugzilla entry is for community support informational purposes only as it does not affect a package in a commercially supported Red Hat product. Refer to the dependent bugs for status of those individual community products.