OpenSSH 3.6.1 and earlier, when restricting host access by numeric IP addresses and with VerifyReverseMapping disabled, allows remote attackers to bypass "from=" and "user@host" address restrictions by connecting to a host from a system whose reverse DNS hostname contains the numeric IP address.

According to its banner, the remote host appears to be running OpenSSH-portable version 3.6.1 or older and is affected by a flaw in such version that could allow an attacker to bypass the access controls set by the administrator of this server.

OpenSSH features a mechanism that can restrict the list of hosts a given user can log from by specifying a pattern in the user key file (ie: *.mynetwork.com would let a user connect only from the local network).

However there is a flaw in the way OpenSSH does reverse DNS lookups. If an attacker configures a DNS server to send a numeric IP address when a reverse lookup is performed, this mechanism could be circumvented.

The version of SunSSH running on the remote host has an information disclosure vulnerability.  A design flaw in the SSH specification could allow a man-in-the-middle attacker to recover up to 32 bits of plaintext from an SSH-protected connection in the standard configuration.  An attacker could exploit this to gain access to sensitive information.

Note that this version of SunSSH is also prone to several additional issues but Nessus did not test for them.

Updated openssh packages that fix several security issues in sshd are now available for Red Hat Enterprise Linux 2.1.

This update has been rated as having important security impact by the Red Hat Security Response Team.

OpenSSH is OpenBSD's SSH (Secure SHell) protocol implementation. This package includes the core files necessary for both the OpenSSH client and server.

Mark Dowd discovered a signal handler race condition in the OpenSSH sshd server. A remote attacker could possibly leverage this flaw to cause a denial of service (crash). (CVE-2006-5051) The OpenSSH project believes the likelihood of successful exploitation leading to arbitrary code execution appears remote. However, the Red Hat Security Response Team have not yet been able to verify this claim due to lack of upstream vulnerability information. We are therefore including a fix for this flaw and have rated it important security severity in the event our continued investigation finds this issue to be exploitable.

Tavis Ormandy of the Google Security Team discovered a denial of service bug in the OpenSSH sshd server. A remote attacker can send a specially crafted SSH-1 request to the server causing sshd to consume a large quantity of CPU resources. (CVE-2006-4924)

An arbitrary command execution flaw was discovered in the way scp copies files locally. It is possible for a local attacker to create a file with a carefully crafted name that could execute arbitrary commands as the user running scp to copy files locally.
(CVE-2006-0225)

The SSH daemon, when restricting host access by numeric IP addresses and with VerifyReverseMapping disabled, allows remote attackers to bypass 'from=' and 'user@host' address restrictions by connecting to a host from a system whose reverse DNS hostname contains the numeric IP address. (CVE-2003-0386)

All users of openssh should upgrade to these updated packages, which contain backported patches that resolve these issues.

Updated openssh packages that fix bugs in sshd are now available for Red Hat Enterprise Linux 3.

This update has been rated as having low security impact by the Red Hat Security Response Team.

OpenSSH is OpenBSD's SSH (Secure SHell) protocol implementation. This package includes the core files necessary for both the OpenSSH client and server.

An arbitrary command execution flaw was discovered in the way scp copies files locally. It is possible for a local attacker to create a file with a carefully crafted name that could execute arbitrary commands as the user running scp to copy files locally.
(CVE-2006-0225)

The SSH daemon, when restricting host access by numeric IP addresses and with VerifyReverseMapping disabled, allows remote attackers to bypass 'from=' and 'user@host' address restrictions by connecting to a host from a system whose reverse DNS hostname contains the numeric IP address. (CVE-2003-0386)

The following issues have also been fixed in this update :

* If the sshd service was stopped using the sshd init script while the main sshd daemon was not running, the init script would kill other sshd processes, such as the running sessions. For example, this could happen when the 'service sshd stop' command was issued twice.

* When privilege separation was enabled, the last login message was printed only for the root user.

* The sshd daemon was sending messages to the system log from a signal handler when debug logging was enabled. This could cause a deadlock of the user's connection.

All users of openssh should upgrade to these updated packages, which resolve these issues.

According to its banner, the remote host appears to be running OpenSSH-portable version 3.6.1 or older.

There is a flaw in such version that could allow an attacker to bypass the access controls set by the administrator of this server.

OpenSSH features a mechanism that can restrict the list of hosts a given user can log from by specifying a pattern in the user key file (ie: *.mynetwork.com would let a user connect only from the local network).

However there is a flaw in the way OpenSSH does reverse DNS lookups.
If an attacker configures a DNS server to send a numeric IP address when a reverse lookup is performed, this mechanism could be circumvented.

ID	Name	Product	Family	Type	Severity
701171	OpenSSH < 3.6.2 Reverse DNS Lookup Bypass	Nessus Network Monitor	SSH		high
55992	SunSSH < 1.1.1 / 1.3 CBC Plaintext Disclosure	Nessus	Misc.	Remote	critical
22474	RHEL 2.1 : openssh (RHSA-2006:0698)	Nessus	Red Hat Local Security Checks	Local	high
22134	CentOS 3 : openssh (CESA-2006:0298)	Nessus	CentOS Local Security Checks	Local	high
22084	RHEL 3 : openssh (RHSA-2006:0298)	Nessus	Red Hat Local Security Checks	Local	high
11712	OpenSSH < 3.6.2 Reverse DNS Lookup Bypass	Nessus	Misc.	Remote	high

Detections

Analytics

CVE-2003-0386

medium

Tenable Plugins

high

critical

high

high

high

high