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. (CVE-2015-6563)

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. (CVE-2015-6564)

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 found that the OpenSSH ssh-agent, a program to hold private keys used for public key authentication, was vulnerable to password guessing attacks. An attacker able to connect to the agent could use this flaw to conduct a brute-force attack to unlock keys in the ssh-agent.

This update fixes the following bugs :

  - Previously, the sshd_config(5) man page was misleading     and could thus confuse the user. This update improves     the man page text to clearly describe the AllowGroups     feature.

  - The limit for the function for restricting the number of     files listed using the wildcard character (*) that     prevents the Denial of Service (DoS) for both server and     client was previously set too low. Consequently, the     user reaching the limit was prevented from listing a     directory with a large number of files over Secure File     Transfer Protocol (SFTP). This update increases the     aforementioned limit, thus fixing this bug.

  - When the ForceCommand option with a pseudoterminal was     used and the MaxSession option was set to '2',     multiplexed SSH connections did not work as expected.
    After the user attempted to open a second multiplexed     connection, the attempt failed if the first connection     was still open. This update modifies OpenSSH to issue     only one audit message per session, and the user is thus     able to open two multiplexed connections in this     situation.

  - The ssh-copy-id utility failed if the account on the     remote server did not use an sh-like shell. Remote     commands have been modified to run in an sh-like shell,     and ssh-copy-id now works also with non-sh-like shells.

  - Due to a race condition between auditing messages and     answers when using ControlMaster multiplexing, one     session in the shared connection randomly and     unexpectedly exited the connection. This update fixes     the race condition in the auditing code, and     multiplexing connections now work as expected even with     a number of sessions created at once.

In addition, this update adds the following enhancements :

  - As not all Lightweight Directory Access Protocol (LDAP)     servers possess a default schema, as expected by the     ssh-ldap-helper program, this update provides the user     with an ability to adjust the LDAP query to get public     keys from servers with a different schema, while the     default functionality stays untouched.

  - With this enhancement update, the administrator is able     to set permissions for files uploaded using Secure File     Transfer Protocol (SFTP).

  - This update provides the LDAP schema in LDAP Data     Interchange Format (LDIF) format as a complement to the     old schema previously accepted by OpenLDAP.

  - With this update, the user can selectively disable the     Generic Security Services API (GSSAPI) key exchange     algorithms as any normal key exchange.

openssh was updated to fix several security issues and bugs.

These security issues were fixed :

  - CVE-2015-5352: The x11_open_helper function in     channels.c in ssh in OpenSSH when ForwardX11Trusted mode     is not used, lacked a check of the refusal deadline for     X connections, which made it easier for remote attackers     to bypass intended access restrictions via a connection     outside of the permitted time window (bsc#936695).

  - CVE-2015-5600: The kbdint_next_device function in     auth2-chall.c in sshd in OpenSSH did not properly     restrict the processing of keyboard-interactive devices     within a single connection, which made it easier for     remote attackers to conduct brute-force attacks or cause     a denial of service (CPU consumption) via a long and     duplicative list in the ssh -oKbdInteractiveDevices     option, as demonstrated by a modified client that     provides a different password for each pam element on     this list (bsc#938746).

  - CVE-2015-4000: Removed and disabled weak DH groups to     address LOGJAM (bsc#932483).

  - Hardening patch to fix sftp RCE (bsc#903649).

  - CVE-2015-6563: The monitor component in sshd in OpenSSH     accepted extraneous username data in     MONITOR_REQ_PAM_INIT_CTX requests, which allowed local     users to conduct impersonation attacks by leveraging any     SSH login access in conjunction with control of the sshd     uid to send a crafted MONITOR_REQ_PWNAM request, related     to monitor.c and monitor_wrap.c.

  - CVE-2015-6564: Use-after-free vulnerability in the     mm_answer_pam_free_ctx function in monitor.c in sshd in     OpenSSH might have allowed local users to gain     privileges by leveraging control of the sshd uid to send     an unexpectedly early MONITOR_REQ_PAM_FREE_CTX request.

The update package also includes non-security fixes. See advisory for details.

Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

OpenSSH was updated to fix several security issues and bugs.

Please note that due to a bug in the previous shipped openssh version, sshd might not correctly restart. Please verify that the ssh daemon is running after installing this update.

These security issues were fixed :

  - CVE-2015-5352: The x11_open_helper function, when     ForwardX11Trusted mode is not used, lacked a check of     the refusal deadline for X connections, which made it     easier for remote attackers to bypass intended access     restrictions via a connection outside of the permitted     time window. (bsc#936695)

  - CVE-2015-5600: The kbdint_next_device function in     auth2-chall.c in sshd did not properly restrict the     processing of keyboard-interactive devices within a     single connection, which made it easier for remote     attackers to conduct brute-force attacks or cause a     denial of service (CPU consumption) via a long and     duplicative list in the ssh

    -oKbdInteractiveDevices option, as demonstrated by a     modified client that provides a different password for     each pam element on this list. (bsc#938746)

  - CVE-2015-4000: Removed and disabled weak DH groups to     address LOGJAM. (bsc#932483)

  - Hardening patch to fix sftp RCE. (bsc#903649)

  - CVE-2015-6563: The monitor component in sshd accepted     extraneous username data in MONITOR_REQ_PAM_INIT_CTX     requests, which allowed local users to conduct     impersonation attacks by leveraging any SSH login access     in conjunction with control of the sshd uid to send a     crafted MONITOR_REQ_PWNAM request, related to monitor.c     and monitor_wrap.c.

  - CVE-2015-6564: Use-after-free vulnerability in the     mm_answer_pam_free_ctx function in monitor.c in sshd     might have allowed local users to gain privileges by     leveraging control of the sshd uid to send an     unexpectedly early MONITOR_REQ_PAM_FREE_CTX request.

Additional a bug was fixed that could lead to openssh not working in chroot (bsc#947458).

Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

The remote Redhat Enterprise Linux 6 host has packages installed that are affected by multiple vulnerabilities as referenced in the RHSA-2016:0741 advisory.

  - openssh: XSECURITY restrictions bypass under certain conditions in ssh(1) (CVE-2015-5352)

  - openssh: Privilege separation weakness related to PAM support (CVE-2015-6563)

  - openssh: Use-after-free bug related to PAM support (CVE-2015-6564)

  - openssh: possible fallback from untrusted to trusted X11 forwarding (CVE-2016-1908)

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

The remote Oracle Linux 6 host has packages installed that are affected by multiple vulnerabilities as referenced in the ELSA-2016-0741 advisory.

    - CVE-2016-3115: missing sanitisation of input for X11 forwarding (#1317817)

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	名称	产品	系列	发布时间	最近更新时间	严重程度
87567	Scientific Linux Security Update : openssh on SL7.x x86_64 (20151119)	Nessus	Scientific Linux Local Security Checks	2015/12/22	2021/1/14	high
85929	SUSE SLES11 Security Update : openssh (SUSE-SU-2015:1547-1) (Logjam)	Nessus	SuSE Local Security Checks	2015/9/14	2022/12/5	low
86339	SUSE SLED11 / SLES11 Security Update : openssh (SUSE-SU-2015:1695-1) (Logjam)	Nessus	SuSE Local Security Checks	2015/10/12	2022/12/5	low
91073	RHEL 6 : openssh (RHSA-2016:0741)	Nessus	Red Hat Local Security Checks	2016/5/12	2024/4/21	critical
91148	Oracle Linux 6 : openssh (ELSA-2016-0741)	Nessus	Oracle Linux Local Security Checks	2016/5/16	2024/10/22	critical

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