Security Advisory

SSH - CVE-2018-15473
Published: October 11, 2018
Last Update: July 23, 2021

An OpenSSH vulnerability could allow an unauthenticated, remote attacker to determine whether given usernames exist or not on the server. No further information is disclosed and there is no potential impact to availability or integrity. This vulnerability may affect the SSH management plane service of ACOS devices and is addressed in this document.

Item # Vulnerability ID Score Source Score Summary
1 CVE-2018-15473 CVSS 3.0 5.3 Med openssh: User enumeration via malformed packets in authentication requests [1]
Affected Releases

The table below indicates releases of ACOS exposed to these vulnerabilities and ACOS releases that address them. ACOS release families not indicated below are unaffected by these vulnerabilities.

Customers using affected ACOS releases can overcome vulnerability exposures by updating to the indicated resolved release. If the table does not list a corresponding resolved or unaffected release, then no ACOS release update is currently available.

Releases Affected Releases Resolved or Unaffected
4.1.4 – 4.1.4-GR1 4.1.4-GR1-P1, 5.1.0, 5.2.0
4.1.2 – 4.1.2-P4 4.1.2-P5
4.1.1 – 4.1.1-P9 4.1.1-P10
4.1.100 – 4.1.100-P5 4.1.100-P5-SP1
4.1.0 – 4.1.0-P11 4.1.0-P12
3.2.5 – 3.2.5-P5 3.2.5-P6, 5.0.1, 5.0.2
3.2.4 – 3.2.4-P1 3.2.4-P2
3.2.3 – 3.2.3-P5 3.2.3-P6
3.2.2 – 3.2.2-P7 3.2.2-P8
2.8.2 – 2.8.2-Px 4.1.2-P5
2.7.2 – 2.7.2-Px 4.1.0-P12, 4.1.1-P10, 4.1.2-P5, 4.1.4-GR1-P1
2.7.1 – 2.7.1-GR1-Px 4.1.0-P12, 4.1.1-P10, 4.1.2-P5, 4.1.4-GR1-P1
2.6.1-GR1 – 2.6.1-GR1-P16 4.1.0-P12, 4.1.1-P10, 4.1.2-P5, 4.1.4-GR1-P1
Workarounds and Mitigations

Common security best practices in the industry for network appliance management and control planes can enhance protection against remote malicious attacks. Limit the exploitable attack surface for critical, infrastructure, networking equipment through the use of access lists or firewall filters to and from only trusted, administrative networks or hosts.

Software Updates

Software updates that address these vulnerabilities are or will be published at the following URL:

Vulnerability Details

The following table shares brief descriptions of the vulnerabilities addressed in this document.

Vulnerability ID Vulnerability Description

OpenSSH through 7.7 is prone to a user enumeration vulnerability due to not delaying bailout for an invalid authenticating user until after the packet containing the request has been fully parsed, related to auth2-gss.c, auth2-hostbased.c, and auth2-pubkey.c.

Related Links
The following table shares brief descriptions for the vulnerabilities addressed in this document.
Ref # General Link
[1] NIST NVD, CVE-2018-15473


Modification History
Revision Date Description
1.0 October 12, 2018

Initial Publication

2.0 August 8, 2019

Updated affected and resolved releases for 4.1.4-GR1 and 3.x ACOS release families, including addition of 3.2.4 release family.

3.0 October 11, 2019

Added 4.1.100 release family

4.0 July 23, 2021

Added 3.2.5, 5.0.1, 5.0.2, 5.1.0, 5.2.0 release families

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