dbcve.org
Ios XeOperating system · Cisco

CVE-2020-3416

MEDIUM · 6.7 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 →
69/100
Remediation priority · Elevated
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
Multiple vulnerabilities in the initialization routines that are executed during bootup of Cisco IOS XE Software for Cisco ASR 900 Series Aggregation Services Routers with a Route Switch Processor 3 (RSP3) installed could allow an authenticated, local attacker with high privileges to execute persistent code at bootup and break the chain of trust. These vulnerabilities are due to incorrect validations by boot scripts when specific ROM monitor (ROMMON) variables are set. An attacker could exploit these vulnerabilities by copying a specific file to the local file system of an affected device and defining specific ROMMON variables. A successful exploit could allow the attacker to run arbitrary code on the underlying operating system (OS) with root privileges. To exploit these vulnerabilities, an attacker would need to have access to the root shell on the device or have physical access to the device.

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 · moderate confidence

Vulnerabilities in bootup initialization routines of Cisco IOS XE for ASR 900 Series routers with RSP3 allow an authenticated local attacker with high privileges to execute persistent code during bootup. The flaws stem from incorrect validations by boot scripts when specific ROM monitor (ROMMON) variables are set, combined with copying a specific file to the device's local filesystem, enabling arbitrary code execution with root privileges and breaking the chain of trust.

MitigationRestrict physical access to affected devices and limit root shell privileges to trusted personnel only; monitor for unauthorized changes to ROMMON variables; apply Cisco-provided patches for IOS XE when available.

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:= 16.12.1= 17.2

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
High
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:H/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. Confirm device is ASR 900 Series with RSP3
    Run 'show platform' or 'show version' to identify the hardware model and RSP3 module presence
    Affected if Device is not an ASR 900 Series router with RSP3 module, then not affected by this specific vulnerability
  2. Check installed IOS XE version
    Run 'show version' and locate the IOS XE software version string
    Affected if Version is exactly 16.12.1 or 17.2 - these are the affected versions; other versions are not affected
  3. Inspect ROMMON variables for non-default settings
    Access ROMMON mode and run 'set' or 'printenv' to view all ROMMON variables; look for any custom or unexpected variable assignments
    Affected if Non-default ROMMON variables are set - the vulnerability requires specific ROMMON variables to be configured
  4. Check for presence of trigger file on local filesystem
    Run 'dir bootflash:' or 'show file systems' to examine the local filesystem for any unexpected or suspicious files that may have been copied there
    Affected if A specific file has been copied to the device's local filesystem in combination with modified ROMMON variables
  5. Review system logs for unauthorized bootup modifications
    Run 'show logging' or check boot logs for entries indicating unexpected boot scripts, code injection, or privilege escalation during device initialization
    Affected if Logs show execution of unauthorized code during bootup or modification of boot scripts

Device is affected only if it is an ASR 900 Series router with RSP3 module, running IOS XE version 16.12.1 or 17.2, with specific ROMMON variables set AND a trigger file present on the local filesystem - all conditions must be met for the vulnerability to be exploitable.

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

Restrict physical access to affected devices and limit root shell privileges to trusted personnel only; monitor for unauthorized changes to ROMMON variables; apply Cisco-provided patches for IOS XE when available.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation8.0 h
  • Implementation4.0 h
  • Testing12.0 h
  • Review / QA6.0 h
30.0 hours of engineering $5,200
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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-2020-3416 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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