Rule

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Sid
17317

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Summary:
This event is generated when an attempt is made to exploit a known vulnerability in openssh.

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Impact:
Denial of Service. Information disclosure. Loss of integrity. Complete admin access.

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Detailed Information:
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.

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Affected Systems:
openbsd openssh 1.2
openbsd openssh 1.2.1
openbsd openssh 1.2.2
openbsd openssh 1.2.27
openbsd openssh 1.2.3
openbsd openssh 2.1
openbsd openssh 2.1.1
openbsd openssh 2.2
openbsd openssh 2.3
openbsd openssh 2.5
openbsd openssh 2.5.1
openbsd openssh 2.5.2
openbsd openssh 2.9
openbsd openssh 2.9.9
openbsd openssh 2.9.9p2
openbsd openssh 2.9p1
openbsd openssh 2.9p2
openbsd openssh 3.0
openbsd openssh 3.0.1
openbsd openssh 3.0.1p1
openbsd openssh 3.0.2
openbsd openssh 3.0.2p1
openbsd openssh 3.0p1
openbsd openssh 3.1
openbsd openssh 3.1p1
openbsd openssh 3.2
openbsd openssh 3.2.2
openbsd openssh 3.2.2p1
openbsd openssh 3.2.3p1
openbsd openssh 3.3
openbsd openssh 3.3p1
openbsd openssh 3.4
openbsd openssh 3.4p1
openbsd openssh 3.5
openbsd openssh 3.5p1
openbsd openssh 3.6
openbsd openssh 3.6.1
openbsd openssh 3.6.1p1
openbsd openssh 3.6.1p2
openbsd openssh 3.7
openbsd openssh 3.7.1
openbsd openssh 3.7.1p1
openbsd openssh 3.7.1p2
openbsd openssh 3.8
openbsd openssh 3.8.1
openbsd openssh 3.8.1p1
openbsd openssh 3.9
openbsd openssh 3.9.1
openbsd openssh 3.9.1p1
openbsd openssh 4.0
openbsd openssh 4.0p1
openbsd openssh 4.1p1
openbsd openssh 4.2
openbsd openssh 4.2p1
openbsd openssh 4.3
openbsd openssh 4.3p1

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Attack Scenarios:
Many types of buffer overflow exist, this is a generic term that may apply to many circumstances that result in an overflow of some kind. A parameter overflow for example, means that the attacker is able to supply data as a parameter to the execution of a program. When the program expands the supplied data, if the size of the parameter is not correctly checked, it may exceed a set limit allowing the attacker to overflow the buffer and write data into memory.
In a stack overflow, the attacker has the opportunity to overwrite a return memory address which allows them to point the return address to a memory location containing code they wish to execute. This allows the attacker to run code with the full privileges of the program in use. The attacker may also supply the address for a known important call, for example the system() call, with the arguments to the call on the stack. The stack also contains the stack pointer and the frame pointer, overwriting these values may lead to a write-what-where condition.
In a heap overflow, it is possible to overwrite function pointers that may be in memory. This may allow the attacker to execute code in memory by changing the function pointer to move to code of their choosing. This can occur even in programs that do not necessarily use function pointers since they may be left in memory at run time. The heap also contains user data which also becomes visible to the attacker.

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Ease of Attack:
Medium.

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False Positives:
None known.

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False Negatives:
None known.

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Corrective Action:
Upgrade to the latest non-affected version of the software.

Apply the appropriate vendor supplied patches.

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Contributors:
Sourcefire Vulnerability Research Team
This document was generated from data supplied by the National Vulnerability Database. A product of the National Institute of Standards and Technology.
For more information see http://nvd.nist.gov/

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Additional References:

NIST CVE-2006-4924:
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2006-4924
 
Common Weakness Enumeration:
http://cwe.mitre.org/data/definitions/120.html
 
Common Attack Pattern Enumeration and Classification:
http://capec.mitre.org/data/definitions/100.html

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