packet.c in ssh in OpenSSH allows remote attackers to cause a denial of service (crash) by sending an invalid protocol sequence with USERAUTH_SUCCESS before NEWKEYS, which causes newkeys[mode] to be NULL.

The installed version of OpenSSH is prior to 4.5 and is affected by the following vulnerabilities:

 - A client-side NULL pointer dereference, caused by a protocol error from a malicious server, which could cause the client to crash. (CVE-2006-4925)
 - A privilege separation vulnerability exists, which could allow attackers to bypass authentication. The vulnerability is caused by a design error between privileged processes and their child processes. Note that this particular issue is only exploitable when other vulnerabilities are present. (CVE-2006-5794)
 - An attacker that connects to the service before it has finished creating keys could force the keys to be recreated. This could result in a denial of service for any processes that relies on a trust relationship with the server. Note that this particular issue only affects the Apple implementation of OpenSSH on Mac OS X. (CVE-2007-0726)

According to its banner, the remote host is running a version of OpenSSH prior to 4.5.  Versions before 4.5 are affected by the following vulnerabilities :

  - A client-side NULL pointer dereference, caused by a     protocol error from a malicious server, which could     cause the client to crash. (CVE-2006-4925)

  - A privilege separation vulnerability exists, which could     allow attackers to bypass authentication. The     vulnerability is caused by a design error between     privileged processes and their child processes. Note     that this particular issue is only exploitable when     other vulnerabilities are present. (CVE-2006-5794)

  - An attacker that connects to the service before it has     finished creating keys could force the keys to be     recreated. This could result in a denial of service for     any processes that relies on a trust relationship with     the server. Note that this particular issue only affects     the Apple implementation of OpenSSH on Mac OS X.     (CVE-2007-0726)

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.

Several security problems were fixed in OpenSSH :

  - A denial of service problem has been fixed in OpenSSH     which could be used to cause lots of CPU consumption on     a remote openssh server. (CVE-2006-4924)

  - If a remote attacker is able to inject network traffic     this could be used to cause a client connection to     close. (CVE-2006-4925)

  - Fixed an unsafe signal hander reported by Mark Dowd. The     signal handler was vulnerable to a race condition that     could be exploited to perform a pre-authentication     denial of service. This vulnerability could     theoretically lead to pre-authentication remote code     execution if GSSAPI authentication is enabled, but the     likelihood of successful exploitation appears remote.
    (CVE-2006-5051)

  - Fixed a GSSAPI authentication abort that could be used     to determine the validity of usernames on some     platforms. (CVE-2006-5052)

Several security problems were fixed in OpenSSH :

  - CVE-2006-4924: A denial of service problem has been     fixed in OpenSSH which could be used to cause lots of     CPU consumption on a remote openssh server.

  - CVE-2006-4925: If a remote attacker is able to inject     network traffic this could be used to cause a client     connection to close.

  - CVE-2006-5051: Fixed an unsafe signal hander reported by     Mark Dowd. The signal handler was vulnerable to a race     condition that could be exploited to perform a     pre-authentication denial of service. This vulnerability     could theoretically lead to pre-authentication remote     code execution if GSSAPI authentication is enabled, but     the likelihood of successful exploitation appears     remote.

  - CVE-2006-5052: Fixed a GSSAPI authentication abort that     could be used to determine the validity of usernames on     some platforms.

Tavis Ormandy of the Google Security Team discovered a Denial of Service vulnerability in the SSH protocol version 1 CRC compensation attack detector. This could allow a remote unauthenticated attacker to trigger excessive CPU utilization by sending a specially crafted SSH message, which would then deny ssh services to other users or processes (CVE-2006-4924, CVE-2006-4925). Please note that Mandriva ships with only SSH protocol version 2 enabled by default.

Next, an unsafe signal handler was found by Mark Dowd. This signal handler was vulnerable to a race condition that could be exploited to perform a pre-authentication DoS, and theoretically a pre-authentication remote code execution in the case where some authentication methods like GSSAPI are enabled (CVE-2006-5051).

Updated packages have been patched to correct this issue.

The version of OpenSSH running on the remote host is prior to version 4.4. Such versions are affected by multiple vulnerabilities:

 - A race condition exists that may allow an unauthenticated, remote attacker to crash the service or, on portable OpenSSH, possibly execute code on the affected host. Note that successful exploitation requires that GSSAPI authentication be enabled.
 - A flaw exists that may allow an attacker to determine the validity of usernames on some platforms. Note that this issue requires that GSSAPI authentication be enabled.
 - When SSH version 1 is used, an issue can be triggered via an SSH packet that contains duplicate blocks that could result in a loss of availability for the service.
 - On Fedora Core 6 (and possibly other systems), an unspecified vulnerability in the linux_audit_record_event() function allows remote attackers to inject incorrect information into audit logs.

According to its banner, the version of OpenSSH installed on the remote host is affected by multiple vulnerabilities :

  - A race condition exists that may allow an     unauthenticated, remote attacker to crash the service     or, on portable OpenSSH, possibly execute code on the     affected host.  Note that successful exploitation     requires that GSSAPI authentication be enabled.
    
  - A flaw exists that may allow an attacker to determine     the validity of usernames on some platforms. Note that     this issue requires that GSSAPI authentication be     enabled.

  - When SSH version 1 is used, an issue can be triggered     via an SSH packet that contains duplicate blocks that     could result in a loss of availability for the service.

  - On Fedora Core 6 (and possibly other systems), an     unspecified vulnerability in the     linux_audit_record_event() function allows remote     attackers to inject incorrect information into     audit logs.

ID	Name	Product	Family	Severity
701165	OpenSSH < 4.5 Multiple Vulnerabilities	Nessus Network Monitor	SSH	high
44077	OpenSSH < 4.5 Multiple Vulnerabilities	Nessus	Misc.	high
55992	SunSSH < 1.1.1 / 1.3 CBC Plaintext Disclosure	Nessus	Misc.	critical
29538	SuSE 10 Security Update : OpenSSH (ZYPP Patch Number 2184)	Nessus	SuSE Local Security Checks	high
27365	openSUSE 10 Security Update : openssh (openssh-2183)	Nessus	SuSE Local Security Checks	high
24565	Mandrake Linux Security Advisory : openssh (MDKSA-2006:179)	Nessus	Mandriva Local Security Checks	high
3751	OpenSSH < 4.4 Multiple Vulnerabilities	Nessus Network Monitor	SSH	low
22466	OpenSSH < 4.4 Multiple Vulnerabilities	Nessus	Misc.	high

Detections

Analytics

CVE-2006-4925

high

Tenable Plugins

high

high

critical

high

high

high

low

high