The OpenSSH server, as used in Fedora and Red Hat Enterprise Linux 7 and when running in a Kerberos environment, allows remote authenticated users to log in as another user when they are listed in the .k5users file of that user, which might bypass intended authentication requirements that would force a local login.

The remote NewStart CGSL host, running version MAIN 4.05, has openssh-latest packages installed that are affected by multiple vulnerabilities:

  - scp in OpenSSH 4.2p1 allows attackers to execute     arbitrary commands via filenames that contain shell     metacharacters or spaces, which are expanded twice.
    (CVE-2006-0225)

  - sshd in OpenSSH before 4.4, when using the version 1 SSH     protocol, allows remote attackers to cause a denial of     service (CPU consumption) via an SSH packet that     contains duplicate blocks, which is not properly handled     by the CRC compensation attack detector. (CVE-2006-4924)

  - Signal handler race condition in OpenSSH before 4.4     allows remote attackers to cause a denial of service     (crash), and possibly execute arbitrary code if GSSAPI     authentication is enabled, via unspecified vectors that     lead to a double-free. (CVE-2006-5051)

  - Unspecified vulnerability in the sshd Privilege     Separation Monitor in OpenSSH before 4.5 causes weaker     verification that authentication has been successful,     which might allow attackers to bypass authentication.
    NOTE: as of 20061108, it is believed that this issue is     only exploitable by leveraging vulnerabilities in the     unprivileged process, which are not known to exist.
    (CVE-2006-5794)

  - Unspecified vulnerability in the     linux_audit_record_event function in OpenSSH 4.3p2, as     used on Fedora Core 6 and possibly other systems, allows     remote attackers to write arbitrary characters to an     audit log via a crafted username. NOTE: some of these     details are obtained from third party information.
    (CVE-2007-3102)

  - The (1) remote_glob function in sftp-glob.c and the (2)     process_put function in sftp.c in OpenSSH 5.8 and     earlier, as used in FreeBSD 7.3 and 8.1, NetBSD 5.0.2,     OpenBSD 4.7, and other products, allow remote     authenticated users to cause a denial of service (CPU     and memory consumption) via crafted glob expressions     that do not match any pathnames, as demonstrated by glob     expressions in SSH_FXP_STAT requests to an sftp daemon,     a different vulnerability than CVE-2010-2632.
    (CVE-2010-4755)

  - 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     (connection-slot exhaustion) by periodically making many     new TCP connections. (CVE-2010-5107)

  - It was found that OpenSSH did not properly handle     certain AcceptEnv parameter values with wildcard     characters. A remote attacker could use this flaw to     bypass intended environment variable restrictions.
    (CVE-2014-2532)

  - It was discovered that OpenSSH clients did not correctly     verify DNS SSHFP records. A malicious server could use     this flaw to force a connecting client to skip the DNS     SSHFP record check and require the user to perform     manual host verification of the DNS SSHFP record.
    (CVE-2014-2653)

  - It was found that when OpenSSH was used in a Kerberos     environment, remote authenticated users were allowed to     log in as a different user if they were listed in the     ~/.k5users file of that user, potentially bypassing     intended authentication restrictions. (CVE-2014-9278)

  - 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. (CVE-2015-5600)

  - 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. (CVE-2015-8325)

  - An information leak flaw was found in the way the     OpenSSH client roaming feature was implemented. A     malicious server could potentially use this flaw to leak     portions of memory (possibly including private SSH keys)     of a successfully authenticated OpenSSH client.
    (CVE-2016-0777)

  - An access flaw was discovered in OpenSSH; the OpenSSH     client did not correctly handle failures to generate     authentication cookies for untrusted X11 forwarding. A     malicious or compromised remote X application could     possibly use this flaw to establish a trusted connection     to the local X server, even if only untrusted X11     forwarding was requested. (CVE-2016-1908)

  - 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. (CVE-2016-6210)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

It was discovered that OpenSSH clients did not correctly verify DNS SSHFP records. A malicious server could use this flaw to force a connecting client to skip the DNS SSHFP record check and require the user to perform manual host verification of the DNS SSHFP record.
(CVE-2014-2653)

It was found that when OpenSSH was used in a Kerberos environment, remote authenticated users were allowed to log in as a different user if they were listed in the ~/.k5users file of that user, potentially bypassing intended authentication restrictions. (CVE-2014-9278)

The openssh packages have been upgraded to upstream version 6.6.1, which provides a number of bug fixes and enhancements over the previous version.

Bug fixes :

  - An existing /dev/log socket is needed when logging using     the syslog utility, which is not possible for all chroot     environments based on the user's home directories. As a     consequence, the sftp commands were not logged in the     chroot setup without /dev/log in the internal sftp     subsystem. With this update, openssh has been enhanced     to detect whether /dev/log exists. If /dev/log does not     exist, processes in the chroot environment use their     master processes for logging.

  - The buffer size for a host name was limited to 64 bytes.
    As a consequence, when a host name was 64 bytes long or     longer, the ssh-keygen utility failed. The buffer size     has been increased to fix this bug, and ssh-keygen no     longer fails in the described situation.

  - Non-ASCII characters have been replaced by their octal     representations in banner messages in order to prevent     terminal re-programming attacks. Consequently, banners     containing UTF-8 strings were not correctly displayed in     a client. With this update, banner messages are     processed according to RFC 3454, control characters have     been removed, and banners containing UTF-8 strings are     now displayed correctly.

  - Scientific Linux uses persistent Kerberos credential     caches, which are shared between sessions. Previously,     the GSSAPICleanupCredentials option was set to 'yes' by     default. Consequently, removing a Kerberos cache on     logout could remove unrelated credentials of other     sessions, which could make the system unusable. To fix     this bug, GSSAPICleanupCredentials is set by default to     'no'.

  - Access permissions for the /etc/ssh/moduli file were set     to 0600, which was unnecessarily strict. With this     update, the permissions for /etc/ssh/moduli have been     changed to 0644 to make the access to the file easier.

  - Due to the KRB5CCNAME variable being truncated, the     Kerberos ticket cache was not found after login using a     Kerberos-enabled SSH connection. The underlying source     code has been modified to fix this bug, and Kerberos     authentication works as expected in the described     situation.

Enhancements :

  - When the sshd daemon is configured to force the internal     SFTP session, a connection other then SFTP is used, the     appropriate message is logged to the /var/log/secure     file.

  - The sshd-keygen service was run using the     'ExecStartPre=-/usr/sbin/sshd- keygen' option in the     sshd.service unit file. With this update, the separate     sshd-keygen.service unit file has been added, and     sshd.service has been adjusted to require     sshd-keygen.service.

Updated openssh packages that fix two security issues, several bugs, and add various enhancements are now available for Red Hat Enterprise Linux 7.

Red Hat Product Security has rated this update as having Moderate security impact. Common Vulnerability Scoring System (CVSS) base scores, which give detailed severity ratings, are available for each vulnerability from the CVE links in the References section.

OpenSSH is OpenBSD's SSH (Secure Shell) protocol implementation. These packages include the core files necessary for both the OpenSSH client and server.

It was discovered that OpenSSH clients did not correctly verify DNS SSHFP records. A malicious server could use this flaw to force a connecting client to skip the DNS SSHFP record check and require the user to perform manual host verification of the DNS SSHFP record.
(CVE-2014-2653)

It was found that when OpenSSH was used in a Kerberos environment, remote authenticated users were allowed to log in as a different user if they were listed in the ~/.k5users file of that user, potentially bypassing intended authentication restrictions. (CVE-2014-9278)

The openssh packages have been upgraded to upstream version 6.6.1, which provides a number of bug fixes and enhancements over the previous version. (BZ#1059667)

Bug fixes :

* An existing /dev/log socket is needed when logging using the syslog utility, which is not possible for all chroot environments based on the user's home directories. As a consequence, the sftp commands were not logged in the chroot setup without /dev/log in the internal sftp subsystem. With this update, openssh has been enhanced to detect whether /dev/log exists. If /dev/log does not exist, processes in the chroot environment use their master processes for logging.
(BZ#1083482)

* The buffer size for a host name was limited to 64 bytes. As a consequence, when a host name was 64 bytes long or longer, the ssh-keygen utility failed. The buffer size has been increased to fix this bug, and ssh-keygen no longer fails in the described situation.
(BZ#1097665)

* Non-ASCII characters have been replaced by their octal representations in banner messages in order to prevent terminal re-programming attacks. Consequently, banners containing UTF-8 strings were not correctly displayed in a client. With this update, banner messages are processed according to RFC 3454, control characters have been removed, and banners containing UTF-8 strings are now displayed correctly. (BZ#1104662)

* Red Hat Enterprise Linux uses persistent Kerberos credential caches, which are shared between sessions. Previously, the GSSAPICleanupCredentials option was set to 'yes' by default.
Consequently, removing a Kerberos cache on logout could remove unrelated credentials of other sessions, which could make the system unusable. To fix this bug, GSSAPICleanupCredentials is set by default to 'no'. (BZ#1134447)

* Access permissions for the /etc/ssh/moduli file were set to 0600, which was unnecessarily strict. With this update, the permissions for /etc/ssh/moduli have been changed to 0644 to make the access to the file easier. (BZ#1134448)

* Due to the KRB5CCNAME variable being truncated, the Kerberos ticket cache was not found after login using a Kerberos-enabled SSH connection. The underlying source code has been modified to fix this bug, and Kerberos authentication works as expected in the described situation. (BZ#1161173)

Enhancements :

* When the sshd daemon is configured to force the internal SFTP session, a connection other then SFTP is used, the appropriate message is logged to the /var/log/secure file. (BZ#1130198)

* The sshd-keygen service was run using the 'ExecStartPre=-/usr/sbin/sshd-keygen' option in the sshd.service unit file. With this update, the separate sshd-keygen.service unit file has been added, and sshd.service has been adjusted to require sshd-keygen.service. (BZ#1134997)

Users of openssh are advised to upgrade to these updated packages, which correct these issues and add these enhancements.

The remote Oracle Linux 7 host has packages installed that are affected by multiple vulnerabilities as referenced in the ELSA-2015-0425 advisory.

    - add new option GSSAPIEnablek5users and disable using ~/.k5users by default CVE-2014-9278       (#1169843)
    - prevent a server from skipping SSHFP lookup - CVE-2014-2653 (#1081338)

Tenable has extracted the preceding description block directly from the Oracle Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Severity
127415	NewStart CGSL MAIN 4.05 : openssh-latest Multiple Vulnerabilities (NS-SA-2019-0146)	Nessus	NewStart CGSL Local Security Checks	critical
82258	Scientific Linux Security Update : openssh on SL7.x x86_64 (20150305)	Nessus	Scientific Linux Local Security Checks	medium
81894	CentOS 7 : openssh (CESA-2015:0425)	Nessus	CentOS Local Security Checks	medium
81725	Oracle Linux 7 : openssh (ELSA-2015-0425)	Nessus	Oracle Linux Local Security Checks	critical
81635	RHEL 7 : openssh (RHSA-2015:0425)	Nessus	Red Hat Local Security Checks	medium

Detections

Analytics

CVE-2014-9278

high

Tenable Plugins

critical

medium

medium

critical

medium