Dropbear sshd versions 2015.71 and below suffer from a command injection vulnerability via xauth. An authenticated user may inject arbitrary xauth commands by sending an x11 channel request that includes a newline character in the x11 cookie. The newline acts as a command separator to the xauth binary. This attack requires the server to have 'X11Forwarding yes' enabled. Disabling it, mitigates this vector.
8129326c102e22e1da62a2fd903c2546c85eba1fd49af454ec0eeb8768c919e3OpenSSH 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.
e76185809315ccb4de20af9908f94cf1d0c88a604c2850502c670e5b10961415Red Hat Security Advisory 2016-2588-02 - 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. Security Fix: It was discovered that the OpenSSH sshd daemon fetched PAM environment settings before running the login program. In configurations with UseLogin=yes and the pam_env PAM module configured to read user environment settings, a local user could use this flaw to execute arbitrary code as root.
e42f57140a7efe5fbed26ea299866c70053ee97e49db3eaf4d90707a4f1db249Debian Linux Security Advisory 3626-1 - Eddie Harari reported that the OpenSSH SSH daemon allows user enumeration through timing differences when trying to authenticate users. When sshd tries to authenticate a non-existing user, it will pick up a fixed fake password structure with a hash based on the Blowfish algorithm. If real users passwords are hashed using SHA256/SHA512, then a remote attacker can take advantage of this flaw by sending large passwords, receiving shorter response times from the server for non-existing users.
2f863fa4086db0a31226d56604fd7475efd80aac9d83230c52c988d3925ce6d0OpenSSHD versions 7.2p2 and below remote username enumeration exploit.
2f182c8354b3885f9f53dee4dfd49de6b64a388306dc36b6cf716adfc0ef8ac9OpenSSHD versions 7.2p2 and below user enumeration exploit.
b69a28b747a4fe5a117cdc11aded97dd15df51cde6788bd96001aa8f57bc36a6Debian Linux Security Advisory 3550-1 - enabled and the sshd PAM configuration is configured to read user- specified environment variables and the "UseLogin" option is enabled, a local user may escalate her privileges to root.
374089592e1cd2eb80c2dec50b28b14a5c1a6f12066de2e2c148453d945875cfRed Hat Security Advisory 2016-0466-01 - OpenSSH is OpenBSD's SSH protocol implementation. These packages include the core files necessary for both the OpenSSH client and server. It was discovered that the OpenSSH server did not sanitize data received in requests to enable X11 forwarding. An authenticated client with restricted SSH access could possibly use this flaw to bypass intended restrictions. It was discovered that the OpenSSH sshd daemon did not check the list of keyboard-interactive authentication methods for duplicates. A remote attacker could use this flaw to bypass the MaxAuthTries limit, making it easier to perform password guessing attacks.
93381a3609cbd40ea19fd90f3d6532393c3c33d49bf30bab516193963789fd55Red Hat Security Advisory 2015-2088-06 - OpenSSH is OpenBSD's SSH protocol implementation. These packages include the core files necessary for both the OpenSSH client and server. A flaw was found in the way OpenSSH handled PAM authentication when using privilege separation. An attacker with valid credentials on the system and able to fully compromise a non-privileged pre-authentication process using a different flaw could use this flaw to authenticate as other users. A use-after-free flaw was found in OpenSSH. An attacker able to fully compromise a non-privileged pre-authentication process using a different flaw could possibly cause sshd to crash or execute arbitrary code with root privileges.
969133ceccf94cfbbd19259f9b16682286538b1be6ef824cd26361a6825383a7freeSSHd version 1.3.1 suffers from a denial of service vulnerability.
394f6434e00eb05d1952d269485e3c3a636bd930a41c5b68ab983b352e8c2632FreeBSD Security Advisory - A programming error in the privileged monitor process of the sshd(8) service may allow the username of an already-authenticated user to be overwritten by the unprivileged child process. A use-after-free error in the privileged monitor process of he sshd(8) service may be deterministically triggered by the actions of a compromised unprivileged child process. A use-after-free error in the session multiplexing code in the sshd(8) service may result in unintended termination of the connection.
3a8b1bfd85b5a339a84d61427764656f8de8bc6b1e993e98a5732638aac6f504Mandriva Linux Security Advisory 2015-095 - sshd in OpenSSH before 6.6 does not properly support wildcards on AcceptEnv lines in sshd_config, which allows remote attackers to bypass intended environment restrictions by using a substring located before a wildcard character. Matthew Vernon reported that if a SSH server offers a HostCertificate that the ssh client doesn't accept, then the client doesn't check the DNS for SSHFP records. As a consequence a malicious server can disable SSHFP-checking by presenting a certificate.
704f97d77be07b02b98aa395298a8190003a67ae5101733fa1d6b66750ddbc2aFreeBSD Security Advisory - Although OpenSSH is not multithreaded, when OpenSSH is compiled with Kerberos support, the Heimdal libraries bring in the POSIX thread library as a dependency. Due to incorrect library ordering while linking sshd(8), symbols in the C library which are shadowed by the POSIX thread library may not be resolved correctly at run time. Note that this problem is specific to the FreeBSD build system and does not affect other operating systems or the version of OpenSSH available from the FreeBSD ports tree. An incorrectly linked sshd(8) child process may deadlock while handling an incoming connection. The connection may then time out or be interrupted by the client, leaving the deadlocked sshd(8) child process behind. Eventually, the sshd(8) parent process stops accepting new connections. An attacker may take advantage of this by repeatedly connecting and then dropping the connection after having begun, but not completed, the authentication process.
8268d282b64535e24bba05832891f3e53bd3a51e05846e68a5926dd47bf5e566bl0wsshd00r backdoors OpenSSH 6.7p1 with a magic password for any user, sniffs and records traffic, and mitigates logging to lastlog/wtmp/utmp.
17bb28d0c4a3e2058cf728936b45586915c671f6cadd0920f2e695332adabeb7Mandriva Linux Security Advisory 2014-068 - sshd in OpenSSH before 6.6 does not properly support wildcards on AcceptEnv lines in sshd_config, which allows remote attackers to bypass intended environment restrictions by using a substring located before a wildcard character. Matthew Vernon reported that if a SSH server offers a HostCertificate that the ssh client doesn't accept, then the client doesn't check the DNS for SSHFP records. As a consequence a malicious server can disable SSHFP-checking by presenting a certificate.
0cf7a48470f92f54508eabbd4f9e1e0ae23f32cf46918fd1489cc6e856cf1a08Ubuntu Security Notice 2104-1 - Florian Sagar discovered that the LXC sshd template set incorrect mount permissions. An attacker could possibly use this flaw to cause privilege escalation on the host.
55cee8e599573f7517c6322a49989c4e8be7e8bd614c71c20266b479497f168aRed Hat Security Advisory 2013-1591-02 - OpenSSH is OpenBSD's Secure Shell protocol implementation. These packages include the core files necessary for the OpenSSH client and server. The default OpenSSH configuration made it easy for remote attackers to exhaust unauthorized connection slots and prevent other users from being able to log in to a system. This flaw has been addressed by enabling random early connection drops by setting MaxStartups to 10:30:100 by default. For more information, refer to the sshd_config man page. These updated openssh packages include numerous bug fixes and enhancements. Space precludes documenting all of these changes in this advisory. Users are directed to the Red Hat Enterprise Linux 6.5 Technical Notes, linked to in the References, for information on the most significant of these changes.
a4f28ff7392407cc2b25c64fb8ce70d6d9dd9cbe74095327d51804e531223977FreeBSD Security Advisory - A memory corruption vulnerability exists in the post-authentication sshd process when an AES-GCM cipher (aes128-gcm@openssh.com or aes256-gcm@openssh.com) is selected during key exchange. If exploited, this vulnerability might permit code execution with the privileges of the authenticated user, thereby allowing a malicious user with valid credentials to bypass shell or command restrictions placed on their account.
878536e73df64b2ee9e3165866803aec2f9d6c286c5bb0c627ff2c9aed8e06feA memory corruption vulnerability exists in the post- authentication sshd process when an AES-GCM cipher (aes128-gcm@openssh.com or aes256-gcm@openssh.com) is selected during kex exchange. If exploited, this vulnerability might permit code execution with the privileges of the authenticated user and may therefore allow bypassing restricted shell/command configurations. OpenSSH versions 6.2 and 6.3 are affected when built against an OpenSSL that supports AES-GCM.
5a14ae6163dbd1bc2080d2d9e5abbece4f4a06fb6c639b17aeb2e9819c2b20d2Mikrotik RouterOS versions 5.x and 6.x suffer from an sshd remote pre-authentication heap corruption vulnerability. Included is a 50 meg Mikrotik package that includes all research items.
74610d5d75efcfb4a984b83085a1bd9e64779bd5d156fb3a81b92d7bb3439349Mandriva Linux Security Advisory 2013-022 - The auth_parse_options function in auth-options.c in sshd in OpenSSH before 5.7 provides debug messages containing authorized_keys command options, which allows remote authenticated users to obtain potentially sensitive information by reading these messages, as demonstrated by the shared user account required by Gitolite. NOTE: this can cross privilege boundaries because a user account may intentionally have no shell or filesystem access, and therefore may have no supported way to read an authorized_keys file in its own home directory. The default configuration of OpenSSH through 6.1 enforces a fixed time limit between establishing a TCP connection and completing a login, which makes it easier for remote attackers to cause a denial of service by periodically making many new TCP connections. The updated packages have been patched to correct these issues.
bee473f9707063a23fbf49f1f2986f75bfe44988e5231b688428c1c9f062130bThis Metasploit module exploits a vulnerability found in FreeSSHd versions 1.2.6 and below to bypass authentication. You just need the username (which defaults to root). The exploit has been tested with both password and public key authentication.
0272e1bc1c0f2058ce2f21fa14e3a0637074e73625db7d48068910d45f94ec8dFreeSSHD suffers from a remote authentication bypass vulnerability.
0f3bd20a3e70422b385aedbcf9be79dcffb498416d75c29e1820bbafa68dab21The RaspberryPi Occidentalis version 0.1 image spawns sshd by default without prompting users to change their credentials, leaving their systems accessible via root/root default credentials.
656c7ec055e2f82105589240af2b020366360c6deae390094ae0d32f88f6c389This is a fake sshd which can be used to log common login attempts which are typically used by scammers / spammers / script kiddies to attempt to gain access to servers. It does not modify OpenSSH and uses libssh instead. There is no valid way to login to a shell, can be used to tarpit / delay attackers and can be used to steal the entries used in a dictionary attack.
2cae65ecac170b8d18902634e1d32ed99b5ad3fc094c4e1979ffdde16083f3edFreeSSHD remote denial of service proof of concept exploit.
64ef29a432819a28b41d8f37b7d65cc811d1a982933c6caf1642e4ced0608e7a
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