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Asr 5000 Series SoftwareApplication · Cisco

CVE-2016-1335

HIGH · 7.5 CVSS v3.0 Published 2016-02-19
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
81/100
Remediation priority · High
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The SSH implementation in Cisco StarOS before 19.3.M0.62771 and 20.x before 20.0.M0.62768 on ASR 5000 devices mishandles a multi-user public-key authentication configuration, which allows remote authenticated users to gain privileges by establishing a connection from an endpoint that was previously used for an administrator's connection, aka Bug ID CSCux22492.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The SSH implementation in Cisco StarOS before versions 19.3.M0.62771 and 20.x before 20.0.M0.62768 on ASR 5000 devices has a privilege escalation vulnerability in multi-user public-key authentication. Authenticated users can gain elevated (administrator) privileges by reconnecting from an endpoint (IP address) that was previously used for an administrator's SSH session.

MitigationUpgrade Cisco StarOS on ASR 5000 devices to version 19.3.M0.62771 or later (19.x) or 20.0.M0.62768 or later (20.x). If immediate patching is not possible, consider network segmentation to limit exposure and implement additional SSH connection monitoring.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Asr 5000 Series SoftwareApplication
Affected:= 16.5.2= 17.7.0= 18.4.0= 19.0.1= 19.3.0= 20.0.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify StarOS version on the ASR 5000
    Run 'show version' or 'show software' command in the StarOS CLI to retrieve the installed software version
    Affected if The version displayed is 16.5.2, 17.7.0, 18.4.0, 19.0.1, 19.3.0, 20.0.0 or any earlier version in the 16.x, 17.x, 18.x, 19.x, or 20.x branches prior to the fixed releases (19.3.M0.62771 or 20.0.M0.62768)
  2. Confirm SSH service is enabled
    Run 'show configuration | include ssh' or 'show ssh server' to check if SSH server is active on the device
    Affected if SSH is enabled and the device is running an affected StarOS version listed above
  3. Verify multi-user public-key authentication is configured
    Run 'show configuration | include auth' or check the AAA configuration for public-key authentication methods. Look for 'public-key' in the authentication login configuration
    Affected if Public-key authentication is configured for SSH users on the device
  4. Review active and recent SSH session records
    Run 'show ssh sessions' or 'show login history' to see current SSH connections and their source IP addresses, particularly noting any IP addresses shared between administrator and non-administrator accounts
    Affected if Multiple users (including administrators) have connected from the same source IP address, indicating potential for the IP reuse privilege escalation
  5. Check privilege assignment for authenticated users
    Run 'show configuration | include privilege' or review user privilege levels in the AAA configuration to confirm users are assigned different privilege levels (e.g., administrator vs. operator)
    Affected if Multiple privilege levels exist and SSH public-key authentication is in use, with the device running an affected version

The device is affected if it is a Cisco ASR 5000 running a vulnerable StarOS version (16.x through 20.x prior to the fixed releases) with SSH multi-user public-key authentication enabled, and there are shared IP addresses between administrator and regular user SSH sessions.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Cisco StarOS on ASR 5000 devices to version 19.3.M0.62771 or later (19.x) or 20.0.M0.62768 or later (20.x). If immediate patching is not possible, consider network segmentation to limit exposure and implement additional SSH connection monitoring.

Fix this in Asr 5000 Series Software Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2016-1335 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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