CVE-2015-2318

The TLS stack in Mono before 3.12.1 allows man-in-the-middle attackers to conduct message skipping attacks and consequently impersonate clients by leveraging missing handshake state validation, aka a "SMACK SKIP-TLS" issue.

A TLS impersonation attack was discovered in Mono's TLS stack by researchers at Inria (CVE-2015-2318). During checks on the TLS stack, they have discovered two further issues which have been fixed, a vulnerability to a protocol downgrade attack (CVE-2015-2319) and SSLv2 support still being available (CVE-2013-2320).

These are all security issues fixed in the ibm-data-db2-4.6.2-1.1 package on the GA media of openSUSE Tumbleweed.

This update adds handling of SHA256 hashes to parts of the X509 Certificate classes in the C# implementation of Mono (bnc#871362) and improves handling of non-existing certificate revocation lists (bnc#810747, bnc#606002).

It was discovered that the Mono TLS implementation was vulnerable to the SKIP-TLS vulnerability. A remote attacker could possibly use this issue to perform client impersonation attacks. (CVE-2015-2318)

It was discovered that the Mono TLS implementation was vulnerable to the FREAK vulnerability. A remote attacker or a machine-in-the-middle could possibly use this issue to force the use of insecure ciphersuites. (CVE-2015-2319)

It was discovered that the Mono TLS implementation still supported a fallback to SSLv2. This update removes the functionality as use of SSLv2 is known to be insecure. (CVE-2015-2320)

It was discovered that Mono incorrectly handled memory in certain circumstances. A remote attacker could possibly use this issue to cause Mono to crash, resulting in a denial of service, or to obtain sensitive information. This issue only applied to Ubuntu 12.04 LTS. (CVE-2011-0992)

It was discovered that Mono incorrectly handled hash collisions. A remote attacker could possibly use this issue to cause Mono to crash, resulting in a denial of service. This issue only applied to Ubuntu 12.04 LTS. (CVE-2012-3543)