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Ios XeApplication · Cisco

CVE-2020-3404

HIGH · 7.8 CVSS v3.1 Published 2020-09-24
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
80/100
Remediation priority · High
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
A vulnerability in the persistent Telnet/Secure Shell (SSH) CLI of Cisco IOS XE Software could allow an authenticated, local attacker to gain shell access on an affected device and execute commands on the underlying operating system (OS) with root privileges. The vulnerability is due to insufficient enforcement of the consent token in authorizing shell access. An attacker could exploit this vulnerability by authenticating to the persistent Telnet/SSH CLI on an affected device and requesting shell access. A successful exploit could allow the attacker to gain shell access on the affected device and execute commands on the underlying OS with root privileges.

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

A local privilege escalation vulnerability in Cisco IOS XE Software's persistent Telnet/SSH CLI allows an authenticated attacker with valid CLI credentials to bypass consent token enforcement and gain root shell access on the underlying operating system. The attacker exploits insufficient authorization checks when requesting shell access through the CLI.

MitigationApply the Cisco IOS XE software update that addresses the consent token enforcement vulnerability. Ensure local CLI accounts follow least-privilege principles and monitor for unauthorized shell access attempts.

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
Ios XeApplication
Affected:= 16.11.1

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
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/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 the device OS and version
    Run 'show version' or 'show inventory' command to identify the software version running on the device
    Affected if The device runs Cisco IOS XE version 16.11.1 exactly
  2. Confirm Telnet or SSH CLI access is enabled
    Run 'show line' or check the configuration with 'show running-config | include (telnet|ssh|vty)' to see if vty lines are configured for Telnet or SSH access
    Affected if Telnet or SSH vty lines are active and accessible
  3. Verify local CLI user accounts exist
    Run 'show running-config | include username' to list locally configured user accounts
    Affected if Local user accounts are configured on the device
  4. Check for consent token configuration
    Examine the configuration with 'show running-config | include consent' or check if privilege escalation prompts are properly configured
    Affected if Consent token enforcement appears missing or misconfigured for shell access requests
  5. Audit recent privilege escalation attempts
    Review system logs and command history with 'show logging' or check for any unexpected shell sessions
    Affected if Logs show unauthorized shell access or privilege escalation from CLI user to root

The environment is affected if the device runs Cisco IOS XE version 16.11.1 with Telnet or SSH CLI access enabled and local user accounts configured, allowing an authenticated attacker to bypass consent token enforcement and gain root shell access.

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

Apply the Cisco IOS XE software update that addresses the consent token enforcement vulnerability. Ensure local CLI accounts follow least-privilege principles and monitor for unauthorized shell access attempts.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,600
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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-2020-3404 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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data