OpenVPN/openvpn v2.6.7 on GitHub

Security Fixes

CVE-2023-46850 OpenVPN versions between 2.6.0 and 2.6.6 incorrectly use a send buffer after it has been free()d in some circumstances, causing some free()d memory to be sent to the peer. All configurations using TLS (e.g. not using --secret) are affected by this issue. (found while tracking down CVE-2023-46849 / Github #400, #417)
CVE-2023-46849 OpenVPN versions between 2.6.0 and 2.6.6 incorrectly restore --fragment configuration in some circumstances, leading to a division by zero when --fragment is used. On platforms where division by zero is fatal, this will cause an OpenVPN crash. (Github #400, #417).

DCO: warn if DATA_V1 packets are sent by the other side - this a hard incompatibility between a 2.6.x client connecting to a 2.4.0-2.4.4 server, and the only fix is to use --disable-dco.
Remove OpenSSL Engine method for loading a key. This had to be removed because the original author did not agree to relicensing the code with the new linking exception added. This was a somewhat obsolete feature anyway as it only worked with OpenSSL 1.x, which is end-of-support.
add warning if p2p NCP client connects to a p2mp server - this is a combination that used to work without cipher negotiation (pre 2.6 on both ends), but would fail in non-obvious ways with 2.6 to 2.6.
add warning to --show-groups that not all supported groups are listed (this is due the internal enumeration in OpenSSL being a bit weird, omitting X448 and X25519 curves).
--dns: remove support for exclude-domains argument (this was a new 2.6 option, with no backend support implemented yet on any platform, and it turns out that no platform supported it at all - so remove option again)
warn user if INFO control message too long, do not forward to management client (safeguard against protocol-violating server implementations)

DCO-WIN: get and log driver version (for easier debugging).
print "peer temporary key details" in TLS handshake
log OpenSSL errors on failure to set certificate, for example if the algorithms used are in acceptable to OpenSSL (misleading message would be printed in cryptoapi / pkcs11 scenarios)
add CMake build system for MinGW and MSVC builds
remove old MSVC build system
improve cmocka unit test building for Windows

Windows Client: Community MSI installer for Windows client can be found at Community Downloads.

Linux Packages: Instructions for installing community-maintained Linux packages can be found in the Community Wiki.

Full Changelog: v2.6.6...v2.6.7