Ubuntu Security Notice 3538-1 - Jann Horn discovered that OpenSSH incorrectly loaded PKCS#11 modules from untrusted directories. A remote attacker could possibly use this issue to execute arbitrary PKCS#11 modules. This issue only affected Ubuntu 14.04 LTS and Ubuntu 16.04 LTS. Jann Horn discovered that OpenSSH incorrectly handled permissions on Unix-domain sockets when privilege separation is disabled. A local attacker could possibly use this issue to gain privileges. This issue only affected Ubuntu 16.04 LTS. Various other issues were also addressed.
964c48c0439d989a11cbdd7601e6770b0c099bed3a91031d5cd9afb0716a4b35Apple Security Advisory 2017-03-27-3 - macOS Sierra 10.12.4, Security Update 2017-001 El Capitan, and Security Update 2017-001 Yosemite are now available and address multiple vulnerabilities.
54a3d5f1eafce35231db5001f3683c3b0fd1ddc198a138e24dfe71082667f5b2FreeBSD Security Advisory - The ssh-agent(1) agent supports loading a PKCS#11 module from outside a trusted whitelist. An attacker can request loading of a PKCS#11 module across forwarded agent-socket. When privilege separation is disabled, forwarded Unix domain sockets would be created by sshd(8) with the privileges of 'root' instead of the authenticated user. A remote attacker who have control of a forwarded agent-socket on a remote system and have the ability to write files on the system running ssh-agent(1) agent can run arbitrary code under the same user credential. Because the attacker must already have some control on both systems, it is relatively hard to exploit this vulnerability in a practical attack. When privilege separation is disabled (on FreeBSD, privilege separation is enabled by default and has to be explicitly disabled), an authenticated attacker can potentially gain root privileges on systems running OpenSSH server.
4133c1c854c216326a44e20a387db0ea0e155db8534256aeaf099421a5c4ce6eSlackware Security Advisory - New openssh packages are available for Slackware 13.0, 13.1, 13.37, 14.0, 14.1, 14.2, and -current to fix security issues.
08ef340d91b270b8a32c5ac63fe7a91ea30387ba285683f09907414b82c6ca39OpenSSH can forward TCP sockets and UNIX domain sockets. If privilege separation is disabled, then on the server side, the forwarding is handled by a child of sshd that has root privileges. For TCP server sockets, sshd explicitly checks whether an attempt is made to bind to a low port (below IPPORT_RESERVED) and, if so, requires the client to authenticate as root. However, for UNIX domain sockets, no such security measures are implemented. This means that, using "ssh -L", an attacker who is permitted to log in as a normal user over SSH can effectively connect to non-abstract unix domain sockets with root privileges. On systems that run systemd, this can for example be exploited by asking systemd to add an LD_PRELOAD environment variable for all following daemon launches and then asking it to restart cron or so. The attached exploit demonstrates this - if it is executed on a system with systemd where the user is allowed to ssh to his own account and where privsep is disabled, it yields a root shell.
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