2018-01 Security Bulletin: Junos OS: OpenSSH Memory exhaustion due to unregistered KEXINIT handler (CVE-2016-8858)

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Product Affected:
This issue affects Junos OS 12.3X48, 15.1, 15.1X49, 15.1X53, 16.1, 16.2.
Problem:

Remote network based attackers can cause the OpenSSH server on Junos OS to allocate an excessive amount of memory. This can potentially create a denial of service condition for the device.

The issue only occurs if SSH is enabled. An attacker must be able to first establish a connection to the SSH service on the device.

This vulnerability can not be triggered from hosts or networks that can not reach the SSH port on the device.

Affected releases are Juniper Networks Junos OS:

  • 12.3X48 versions 12.3X48-D55 and above but prior to 12.3X48-D65;
  • 15.1R5-S4, 15.1R5-S5;
  • 15.1R6;
  • 15.1X49 versions 15.1X49-D100 and above, but prior to 15.1X49-D121;
  • 15.1X53-D57;
  • 16.1 versions prior to 16.1R4-S6, 16.1R5;
  • 16.2 versions prior to 16.2R2.

The issue only affects devices where SSH is enabled.

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

This issue was discovered during an external security research.

This issue has been assigned CVE-2016-8858.

Solution:

The following software releases have been updated to resolve this specific issue: 12.3X48-D65, 15.1R5-S6, 15.1R7, 15.1X49-D121, 16.1R4-S6, 16.1R5, 16.2R2, 17.1R1, 17.2R1, and all subsequent releases.

This issue is being tracked as 1228873 which is visible on the Customer Support website.

Note: Juniper SIRT's policy is not to evaluate releases which are beyond End of Engineering (EOE) or End of Life (EOL).

Workaround:

Use access lists or firewall filters to limit access to the device, so that it can only be accessed from trusted hosts. Restrict access to only highly trusted administrators.

Implementation:
Software Releases, patches and updates are available at https://www.juniper.net/support/downloads/.
Modification History:
2018-01-10: Initial publication
Related Links:
CVSS Score:
5.3 (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L)
Risk Level:
Medium
Risk Assessment:
Information for how Juniper Networks uses CVSS can be found at KB 16446 "Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."