ID CVE-2014-9278
Summary 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.
References
Vulnerable Configurations
  • OpenBSD OpenSSH
    cpe:2.3:a:openbsd:openssh
  • Fedora 7
    cpe:2.3:o:redhat:fedora:7
  • Red Hat Enterprise Linux (RHEL) 7.0 (7)
    cpe:2.3:o:redhat:enterprise_linux:7.0
CVSS
Base: 4.0 (as of 23-12-2014 - 12:24)
Impact:
Exploitability:
CWE CWE-287
CAPEC
  • Authentication Abuse
    An attacker obtains unauthorized access to an application, service or device either through knowledge of the inherent weaknesses of an authentication mechanism, or by exploiting a flaw in the authentication scheme's implementation. In such an attack an authentication mechanism is functioning but a carefully controlled sequence of events causes the mechanism to grant access to the attacker. This attack may exploit assumptions made by the target's authentication procedures, such as assumptions regarding trust relationships or assumptions regarding the generation of secret values. This attack differs from Authentication Bypass attacks in that Authentication Abuse allows the attacker to be certified as a valid user through illegitimate means, while Authentication Bypass allows the user to access protected material without ever being certified as an authenticated user. This attack does not rely on prior sessions established by successfully authenticating users, as relied upon for the "Exploitation of Session Variables, Resource IDs and other Trusted Credentials" attack patterns.
  • Exploiting Trust in Client (aka Make the Client Invisible)
    An attack of this type exploits a programs' vulnerabilities in client/server communication channel authentication and data integrity. It leverages the implicit trust a server places in the client, or more importantly, that which the server believes is the client. An attacker executes this type of attack by placing themselves in the communication channel between client and server such that communication directly to the server is possible where the server believes it is communicating only with a valid client. There are numerous variations of this type of attack.
  • Utilizing REST's Trust in the System Resource to Register Man in the Middle
    This attack utilizes a REST(REpresentational State Transfer)-style applications' trust in the system resources and environment to place man in the middle once SSL is terminated. Rest applications premise is that they leverage existing infrastructure to deliver web services functionality. An example of this is a Rest application that uses HTTP Get methods and receives a HTTP response with an XML document. These Rest style web services are deployed on existing infrastructure such as Apache and IIS web servers with no SOAP stack required. Unfortunately from a security standpoint, there frequently is no interoperable identity security mechanism deployed, so Rest developers often fall back to SSL to deliver security. In large data centers, SSL is typically terminated at the edge of the network - at the firewall, load balancer, or router. Once the SSL is terminated the HTTP request is in the clear (unless developers have hashed or encrypted the values, but this is rare). The attacker can utilize a sniffer such as Wireshark to snapshot the credentials, such as username and password that are passed in the clear once SSL is terminated. Once the attacker gathers these credentials, they can submit requests to the web service provider just as authorized user do. There is not typically an authentication on the client side, beyond what is passed in the request itself so once this is compromised, then this is generally sufficient to compromise the service's authentication scheme.
  • Man in the Middle Attack
    This type of attack targets the communication between two components (typically client and server). The attacker places himself in the communication channel between the two components. Whenever one component attempts to communicate with the other (data flow, authentication challenges, etc.), the data first goes to the attacker, who has the opportunity to observe or alter it, and it is then passed on to the other component as if it was never intercepted. This interposition is transparent leaving the two compromised components unaware of the potential corruption or leakage of their communications. The potential for Man-in-the-Middle attacks yields an implicit lack of trust in communication or identify between two components.
Access
VectorComplexityAuthentication
NETWORK LOW SINGLE_INSTANCE
Impact
ConfidentialityIntegrityAvailability
NONE PARTIAL NONE
nessus via4
  • NASL family Red Hat Local Security Checks
    NASL id REDHAT-RHSA-2015-0425.NASL
    description 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.
    last seen 2017-10-29
    modified 2017-01-06
    plugin id 81635
    published 2015-03-05
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=81635
    title RHEL 7 : openssh (RHSA-2015:0425)
  • NASL family Oracle Linux Local Security Checks
    NASL id ORACLELINUX_ELSA-2015-0425.NASL
    description From Red Hat Security Advisory 2015:0425 : 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.
    last seen 2017-10-29
    modified 2016-05-06
    plugin id 81725
    published 2015-03-10
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=81725
    title Oracle Linux 7 : openssh (ELSA-2015-0425)
  • NASL family Scientific Linux Local Security Checks
    NASL id SL_20150305_OPENSSH_ON_SL7_X.NASL
    description 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.
    last seen 2017-10-29
    modified 2015-03-26
    plugin id 82258
    published 2015-03-26
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=82258
    title Scientific Linux Security Update : openssh on SL7.x x86_64
  • NASL family CentOS Local Security Checks
    NASL id CENTOS_RHSA-2015-0425.NASL
    description 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.
    last seen 2017-10-29
    modified 2016-04-28
    plugin id 81894
    published 2015-03-18
    reporter Tenable
    source https://www.tenable.com/plugins/index.php?view=single&id=81894
    title CentOS 7 : openssh (CESA-2015:0425)
redhat via4
advisories
bugzilla
id 1169843
title CVE-2014-9278 openssh: ~/.k5users unexpectedly grants remote login
oval
AND
  • OR
    • comment Red Hat Enterprise Linux 7 Client is installed
      oval oval:com.redhat.rhsa:tst:20140675001
    • comment Red Hat Enterprise Linux 7 Server is installed
      oval oval:com.redhat.rhsa:tst:20140675002
    • comment Red Hat Enterprise Linux 7 Workstation is installed
      oval oval:com.redhat.rhsa:tst:20140675003
    • comment Red Hat Enterprise Linux 7 ComputeNode is installed
      oval oval:com.redhat.rhsa:tst:20140675004
  • OR
    • AND
      • comment openssh is earlier than 0:6.6.1p1-11.el7
        oval oval:com.redhat.rhsa:tst:20150425005
      • comment openssh is signed with Red Hat redhatrelease2 key
        oval oval:com.redhat.rhsa:tst:20120884006
    • AND
      • comment openssh-askpass is earlier than 0:6.6.1p1-11.el7
        oval oval:com.redhat.rhsa:tst:20150425013
      • comment openssh-askpass is signed with Red Hat redhatrelease2 key
        oval oval:com.redhat.rhsa:tst:20120884008
    • AND
      • comment openssh-clients is earlier than 0:6.6.1p1-11.el7
        oval oval:com.redhat.rhsa:tst:20150425017
      • comment openssh-clients is signed with Red Hat redhatrelease2 key
        oval oval:com.redhat.rhsa:tst:20120884014
    • AND
      • comment openssh-keycat is earlier than 0:6.6.1p1-11.el7
        oval oval:com.redhat.rhsa:tst:20150425011
      • comment openssh-keycat is signed with Red Hat redhatrelease2 key
        oval oval:com.redhat.rhsa:tst:20150425012
    • AND
      • comment openssh-ldap is earlier than 0:6.6.1p1-11.el7
        oval oval:com.redhat.rhsa:tst:20150425007
      • comment openssh-ldap is signed with Red Hat redhatrelease2 key
        oval oval:com.redhat.rhsa:tst:20120884012
    • AND
      • comment openssh-server is earlier than 0:6.6.1p1-11.el7
        oval oval:com.redhat.rhsa:tst:20150425009
      • comment openssh-server is signed with Red Hat redhatrelease2 key
        oval oval:com.redhat.rhsa:tst:20120884016
    • AND
      • comment openssh-server-sysvinit is earlier than 0:6.6.1p1-11.el7
        oval oval:com.redhat.rhsa:tst:20150425015
      • comment openssh-server-sysvinit is signed with Red Hat redhatrelease2 key
        oval oval:com.redhat.rhsa:tst:20150425016
    • AND
      • comment pam_ssh_agent_auth is earlier than 0:0.9.3-9.11.el7
        oval oval:com.redhat.rhsa:tst:20150425019
      • comment pam_ssh_agent_auth is signed with Red Hat redhatrelease2 key
        oval oval:com.redhat.rhsa:tst:20120884010
rhsa
id RHSA-2015:0425
released 2015-03-05
severity Moderate
title RHSA-2015:0425: openssh security, bug fix and enhancement update (Moderate)
rpms
  • openssh-0:6.6.1p1-11.el7
  • openssh-askpass-0:6.6.1p1-11.el7
  • openssh-clients-0:6.6.1p1-11.el7
  • openssh-keycat-0:6.6.1p1-11.el7
  • openssh-ldap-0:6.6.1p1-11.el7
  • openssh-server-0:6.6.1p1-11.el7
  • openssh-server-sysvinit-0:6.6.1p1-11.el7
  • pam_ssh_agent_auth-0:0.9.3-9.11.el7
refmap via4
bid 71420
confirm
misc http://thread.gmane.org/gmane.comp.encryption.kerberos.general/15855
mlist
  • [oss-security] 20141202 CVE request: OpenSSH ~/.k5users patch (Fedora and downstreams)
  • [oss-security] 20141204 Re: CVE request: OpenSSH ~/.k5users patch (Fedora and downstreams)
xf openssh-gssservkrb5-sec-bypass(99090)
Last major update 17-03-2015 - 22:03
Published 06-12-2014 - 10:59
Last modified 07-09-2017 - 21:29
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