It was found that the shared memory manager used by pre-authentication compression support had a bounds checks that could be elided by some optimizing compilers. Additionally, this memory manager was incorrectly accessible when pre-authentication compression was disabled. This could potentially allow attacks against the privileged monitor process from the sandboxed privilege-separation process (a compromise of the latter would be required first).
It was found that the shared memory manager used by pre-authentication compression support had a bounds checks that could be elided by some optimizing compilers. Additionally, this memory manager was incorrectly accessible when pre-authentication compression was disabled. This could potentially allow attacks against the privileged monitor process from the sandboxed privilege-separation process (a compromise of the latter would be required first).
https://www.openssh.com/txt/release-7.4 http://seclists.org/oss-sec/2016/q4/705