dbcve.org
Ios XeOperating system · Cisco

CVE-2021-1375

MEDIUM · 6.7 CVSS v3.1 Published 2021-03-24
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 fast reload feature of Cisco IOS XE Software running on Cisco Catalyst 3850, Cisco Catalyst 9300, and Cisco Catalyst 9300L Series Switches could allow an authenticated, local attacker to either execute arbitrary code on the underlying operating system, install and boot a malicious software image, or execute unsigned binaries on an affected device. These vulnerabilities are due to improper checks performed by system boot routines. To exploit these vulnerabilities, the attacker would need privileged access to the CLI of the device. A successful exploit could allow the attacker to either execute arbitrary code on the underlying operating system or execute unsigned code and bypass the image verification check part of the secure boot process. For more information about these vulnerabilities, see the Details section of this advisory.

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

Vulnerabilities in the fast reload feature of Cisco IOS XE on Catalyst 3850/9300/9300L switches allow an authenticated privileged attacker to execute arbitrary code at the OS level or bypass secure boot image verification through improper checks in system boot routines.

MitigationApply the Cisco IOS XE software update addressing CVE-2021-1375 and limit privileged CLI access to trusted personnel 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:= 16.5.1= 16.5.1a= 16.6.1= 16.6.2= 16.6.3= 16.6.4= 16.6.4a= 16.6.4s= 16.6.5= 16.6.6= 16.6.7= 16.8.1

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
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. Identify the device model
    Run 'show version' or 'show inventory' command and look for Catalyst 3850, Catalyst 9300, or Catalyst 9300L in the output
    Affected if The device is a Catalyst 3850, 9300, or 9300L switch
  2. Confirm the IOS XE version
    Run 'show version' and locate the version string (typically shows 'Version 16.x.x' or similar)
    Affected if The version is exactly 16.5.1, 16.5.1a, 16.6.1, 16.6.2, 16.6.3, 16.6.4, 16.6.4a, 16.6.4s, 16.6.5, 16.6.6, 16.6.7, or 16.8.1
  3. Check for fast reload feature configuration
    Run 'show running-config | include fast-reload' or 'show reload' to see if fast reload is configured or has been used
    Affected if Fast reload feature is enabled or has been configured on the device
  4. Verify privileged access exposure
    Review the current privilege level by running 'show privilege' and check which users have level 15 (privileged exec) access via 'show users'
    Affected if Multiple or untrusted users have privileged (level 15) exec access

A device is affected if it is a Catalyst 3850/9300/9300L running IOS XE version 16.5.1 through 16.8.1 with the fast reload feature available and potential exposure to untrusted privileged users.

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 addressing CVE-2021-1375 and limit privileged CLI access to trusted personnel only.

Fix this in Ios Xe Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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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-2021-1375 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