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Ios XeOperating system · Cisco

CVE-2020-3403

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 CLI of Cisco IOS XE Software could allow an authenticated, local attacker to inject a command to the underlying operating system that will execute with root privileges upon the next reboot of the device. The authenticated user must have privileged EXEC permissions on the device. The vulnerability is due to insufficient protection of values passed to a script that executes during device startup. An attacker could exploit this vulnerability by writing values to a specific file. A successful exploit could allow the attacker to execute commands with root privileges each time the affected device is restarted.

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 allows an authenticated attacker with privileged EXEC permissions to inject commands into a startup script by writing values to a specific file. The injected commands execute with root privileges upon the next device reboot.

MitigationApply the Cisco security patch for CVE-2020-3403 or upgrade to a fixed IOS XE version. Limit physical and administrative access to trusted, privileged users only.

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 XeOperating system
Affected:= 17.2.1

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 installed IOS XE version
    Execute 'show version' or 'show version | include Version' from the CLI to display the running IOS XE version
    Affected if The displayed version matches 17.2.1 exactly (or falls within the specific affected version range if Cisco has published one)
  2. Verify privileged EXEC access configuration
    Execute 'show running-config | include privilege' or check the current privilege level with 'show privilege' to see the configured EXEC privilege levels
    Affected if Multiple user accounts or enable passwords are configured granting privilege level 15 (privileged EXEC) access beyond the intended administrator
  3. Inspect startup configuration files for anomalies
    Execute 'show startup-config' or review the startup script file referenced in the device configuration for unexpected or unauthorized commands, particularly those scheduled to run at system initialization
    Affected if The startup configuration contains commands or scripts that were not intentionally added by the legitimate administrator, especially if they appear to grant elevated privileges or execute unexpected programs
  4. Check for unauthorized users or accounts
    Execute 'show users' and compare against 'show running-config | include username' to identify any unexpected accounts configured on the device
    Affected if There are user accounts configured in the system that were not created by the legitimate administrator, particularly accounts with privilege level 15

The device is likely affected if it runs IOS XE version 17.2.1 (or the specific affected version) and has any unexpected entries in startup scripts or unauthorized privileged accounts present on the system.

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 security patch for CVE-2020-3403 or upgrade to a fixed IOS XE version. Limit physical and administrative access to trusted, privileged users only.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,800
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Scan for this in your stack

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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-2020-3403 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