This Metasploit module uses a malformed packet or timing attack to enumerate users on an OpenSSH server. The default action sends a malformed (corrupted) SSH_MSG_USERAUTH_REQUEST packet using public key authentication (must be enabled) to enumerate users. On some versions of OpenSSH under some configurations, OpenSSH will return a "permission denied" error for an invalid user faster than for a valid user, creating an opportunity for a timing attack to enumerate users. Testing note: invalid users were logged, while valid users were not. YMMV.
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Ubuntu Security Notice 3809-2 - USN-3809-1 fixed vulnerabilities in OpenSSH. The update for CVE-2018-15473 was incomplete and could introduce a regression in certain environments. This update fixes the problem. Robert Swiecki discovered that OpenSSH incorrectly handled certain messages. An attacker could possibly use this issue to cause a denial of service. This issue only affected Ubuntu 14.04 LTS and Ubuntu 16.04 LTS. It was discovered that OpenSSH incorrectly handled certain requests. An attacker could possibly use this issue to access sensitive information. Various other issues were also addressed.
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Red Hat Security Advisory 2019-2143-01 - 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. A user enumeration issue has been addressed.
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Red Hat Security Advisory 2019-0711-01 - 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. A user enumeration vulnerability has been addressed.
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OpenSSH versions prior to 7.7 suffer from a user enumeration vulnerability.
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Ubuntu Security Notice 3809-1 - Robert Swiecki discovered that OpenSSH incorrectly handled certain messages. An attacker could possibly use this issue to cause a denial of service. This issue only affected Ubuntu 14.04 LTS and Ubuntu 16.04 LTS. It was discovered that OpenSSH incorrectly handled certain requests. An attacker could possibly use this issue to access sensitive information. Various other issues were also addressed.
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Gentoo Linux Security Advisory 201810-3 - A vulnerability in OpenSSH might allow remote attackers to determine valid usernames. Versions less than 7.7_p1-r8 are affected.
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Debian Linux Security Advisory 4280-1 - Dariusz Tytko, Michal Sajdak and Qualys Security discovered that OpenSSH, an implementation of the SSH protocol suite, was prone to a user enumeration vulnerability. This would allow a remote attacker to check whether a specific user account existed on the target server.
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