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OpenSSH IP address restriction bypass
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Secunia Advisory:
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SA8974
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Release Date:
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2003-06-09
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Last Update:
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2003-10-29
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Critical:
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Not critical
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Impact:
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Security Bypass
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Where:
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From remote
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Solution Status:
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Vendor Patch
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| Software: | OpenSSH 3.x
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| | CVE reference: | CVE-2003-0386 (Secunia mirror)
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Description:
A vulnerability has been identified in OpenSSH allowing users to access the system from IPs that they where not supposed to.
OpenSSH allows system administrators to limit access to the service based on hostnames or IP addresses. This may be configured so that specific users may only connect from certain IP addresses or hostnames.
The problem is that OpenSSH doesn't know when the restriction applies to a hostname or an IP. This allows users who controls the reverse DNS answer for their IP address to change their hostname so that it matches an IP address.
This affects versions 3.6.1 and earlier.
NOTE: This does not allow users to connect and authenticate with the service unless they have obtained a valid key or username / password.
Solution:
Do never rely on IP filtering at application level. Always apply IP restrictions using a perimeter firewall, router, iptables or similar.
OpenSSH version 3.6.1 and earlier support the "VerifyReverseMapping" option, which provides an additional verification of the hostname / IP address.
Provided and/or discovered by:
Mike Harding
Other References:
http://www.kb.cert.org/vuls/id/978316
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Please note: The information that this Secunia Advisory is based on comes from a third party unless stated otherwise.
Secunia collects, validates, and verifies all vulnerability reports issued by security research groups, vendors, and others.
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9 Related Secunia Security Advisories
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1. OpenSSH Privilege Separation Monitor Weakness
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2. OpenSSH Signal Handling Vulnerability and User Enumeration Weakness
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3. OpenSSH Identical Blocks Denial of Service Vulnerability
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4. OpenSSH scp Command Line Shell Command Injection
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5. OpenSSH Two Security Issues
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6. OpenSSH PAM implementation Vulnerability
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7. OpenSSH "buffer_append_space()" Buffer Management Vulnerability
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8. OpenSSH User Identification Vulnerability
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9. OpenSSH allows root to read users passwords
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