A TLS impersonation attack was discovered in Mono’s TLS stack by researchers at Inria (SKIP-TLS. During checks on our TLS stack, we have discovered two further issues which we have fixed - SSLv2 support, and vulnerability to FREAK. These vulnerabilities affect basically every Mono version ever released.
All three issues should be addressed in the following patches:
These patches should apply to all Mono versions from 3.4.0 or so onwards. The FREAK patch requires slight modification in order to apply to Mono releases prior to 3.x patch for Mono pre-3.4 should work for these users. The Impersonation patch requires slight modification to apply to Mono releases prior to 3.4 patch for Mono pre-3.4 should work for these users.
Alternatively, this is fixed in Mono 3.12.1 and higher: mono-3.12.1.tar.bz2
Mono’s github repository contains the bug fix for all supported branches (master, mono-4.0.0-branch, mono-3.12.0-branch, mono-3.10.0-branch).
Linux and Mac downloads from mono-project.com have been updated to 3.12.1 - the Windows release will take another day or two.
Below is a (non-exhaustive) list of Mono versions in use in supported distributions, and the patches they require for full coverage.