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.
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Red Hat Security Advisory 2017-2029-01 - OpenSSH is an SSH protocol implementation supported by a number of Linux, UNIX, and similar operating systems. It includes the core files necessary for both the OpenSSH client and server. The following packages have been upgraded to a later upstream version: openssh. Security Fix: A covert timing channel flaw was found in the way OpenSSH handled authentication of non-existent users. A remote unauthenticated attacker could possibly use this flaw to determine valid user names by measuring the timing of server responses.
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Apple 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.
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FreeBSD 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.
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Slackware 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.
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The OpenSSH agent permits its clients to load PKCS11 providers using the commands SSH_AGENTC_ADD_SMARTCARD_KEY and SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED if OpenSSH was compiled with the ENABLE_PKCS11 flag (normally enabled) and the agent isn't locked. For these commands, the client has to specify a provider name. Th e agent passes this provider name to a subprocess (via ssh-agent.c:process_add_smartcard_key -> ssh-pkcs11-client.c:pkcs11_add_provider -> ssh-pkcs11-client.c:s end_msg), and the subprocess receives it and passes it to dlopen() (via ssh-pkcs 11-helper.c:process -> ssh-pkcs11-helper.c:process_add -> ssh-pkcs11.c:pkcs11_ad d_provider -> dlopen). No checks are performed on the provider name, apart from testing whether that provider is already loaded. This means that, if a user connects to a malicious SSH server with agent forwarding enabled and the malicious server has the ability to place a file with attacker-controlled contents in the victim's filesystem, the SSH server can execute code on the user's machine.
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