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2015-12 Out of Cycle Security Bulletin: ScreenOS: Crafted SSH negotiation may trigger system crash (​CVE-2015-7754)

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Article ID: JSA10712 SECURITY_ADVISORIES Last Updated: 17 Dec 2015Version: 2.0
Product Affected:
This issue can affect any product or platform running ScreenOS 6.3.0r20.
Problem:
A crafted SSH negotiation may result in a system crash when ssh-pka is configured and enabled on the firewall. In the worst case scenario, the unhandled SSH exception resulting in a system crash could lead to remote code execution.

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 has been assigned CVE-2015-7754.
Solution:
The following software releases have been updated to resolve this specific issue: ScreenOS 6.3.0r21, and all subsequent releases.

This issue is being tracked as PR 1139205 which 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:
Restrict management access to specific IP addresses.  Refer to KB3905 for more information about restricting management access in ScreenOS.

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 management access to the device only from trusted, administrative networks or hosts.
Implementation:
How to obtain fixed software:
ScreenOS software releases are available at http://www.juniper.net/support/downloads/screenos.html

Modification History:
Modification History:

2015-12-17: Initial publication

CVSS Score:
9.8 (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)
Severity Level:
Critical
Severity Assessment:
Information for how Juniper Networks uses CVSS can be found at KB 16446 "Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."
Acknowledgements:
 

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