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Thursday, October 15, 2015

Junos: Corrupt pam.conf file allows unauthenticated root access

Product Affected:

This issue can affect any product or platform running Junos OS.​​
 
Problem:

When the pam.conf file is corrupted in certain ways, it may allow connection to the device as the root user with no password. This "fail-open" behavior allows an attacker who can specifically modify the file to gain full access to the device.

Note that inadvertent manipulation of the pam.conf by an authorized administrator can also lead to unauthenticated root access to the device. Extreme care should be taken by administrators to avoid modifying pam.conf directly.

While the standalone vulnerability may not be directly exploitable, this issue increases the severity of other attacks that may be chained together to launch a multi-stage advanced attack against the device.

This issue is assigned ​CVE-2015-7751.

Solution:
The following software releases have been updated to resolve this specific issue: Junos OS 12.1X44-D50, 12.1X46-D35, 12.1X47-D25, 12.3R9, 12.3X48-D15, 13.2R7, 13.2X51-D35, 13.3R6, 14.1R5, 14.1X50-D105, 14.1X51-D70, 14.1X53-D25, 14.1X55-D20, 14.2R1, 15.1F2, 15.1R1, 15.1X49-D10, and all subsequent releases.​

This issue was found during internal product security testing.

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

No other Juniper Networks products or platforms are affected by this issue.

This issue is being tracked as PR 965378 and is visible on the Customer Support website.

KB16765 - "In which releases are vulnerabilities fixed?" describes which release vulnerabilities are fixed as per our End of Engineering and End of Life support policies.​​


Workaround:
​Use access lists or firewall filters to limit CLI access to the router only from trusted hosts.

In addition to the recommendations listed above, it is good security practice to limit the exploitable attack surface of critical infrastructure networking equipment. Use access lists or firewall filters to limit access to the router via SSH or telnet only from trusted, administrative networks or hosts.

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