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Sd WanApplication · Cisco

CVE-2021-34726

MEDIUM · 6.7 CVSS v3.1 Published 2021-09-23
Fix available
A fix is available. Upgrade to 18.4.6 / 19.2.3 or later.
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
A vulnerability in the CLI of Cisco SD-WAN Software could allow an authenticated, local attacker to inject arbitrary commands to be executed with root-level privileges on the underlying operating system of an affected device. This vulnerability is due to insufficient input validation on certain CLI commands. An attacker could exploit this vulnerability by authenticating to an affected device and submitting crafted input to the CLI. The attacker must be authenticated as an administrative user to execute the affected commands. A successful exploit could allow the attacker to execute commands with root-level 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 command injection vulnerability in the Cisco SD-WAN CLI allows authenticated administrative users to inject and execute arbitrary OS commands with root-level privileges due to insufficient input validation on certain CLI commands. This is a local, authenticated attack requiring administrative credentials that results in complete privilege escalation to root.

MitigationApply the Cisco patch when available. Until then, strictly limit CLI access to trusted administrative users only, monitor for suspicious command execution, and consider network segmentation to reduce exposure.

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
Sd WanApplication
Affected:< 18.4.6>= 19.2.0, < 19.2.3>= 20.1, < 20.1.2>= 20.3, < 20.3.1>= 20.4, < 20.4.1>= 20.5, < 20.5.1

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 Cisco SD-WAN version
    Log into the SD-WAN CLI and run 'show version' or 'show software version' to obtain the installed software version
    Affected if The installed version falls into any of these ranges: < 18.4.6; >= 19.2.0 and < 19.2.3; >= 20.1 and < 20.1.2; >= 20.3 and < 20.3.1; >= 20.4 and < 20.4.1; >= 20.5 and < 20.5.1
  2. Confirm CLI administrative access is enabled
    Verify that the CLI interface is accessible for administrative users. Check if 'enable' or privileged EXEC mode is available
    Affected if CLI administrative access exists and the version is in the affected range from step 1
  3. Review authentication method
    Check the AAA configuration with 'show running-config | include aaa' or 'show auths' to see how administrative users authenticate to the CLI
    Affected if Local or remote administrative authentication is configured, combined with an affected version, creates the condition for exploitation
  4. Audit CLI command logs
    Review system logs, accounting logs, or use 'show log' for executed CLI commands. Look for unusual or unexpected command patterns that may indicate exploitation attempts
    Affected if Unexpected commands appear in logs, especially from administrative accounts, on an affected version

A user is affected if they are running any Cisco SD-WAN version within the specified vulnerable ranges and have CLI administrative access enabled.

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.

dbcve · scoped
Upgrade available Upgrade to 18.4.6 / 19.2.3 / 20.1.2 or later
Fixed in 18.4.619.2.320.1.2
Interim mitigation

Apply the Cisco patch when available. Until then, strictly limit CLI access to trusted administrative users only, monitor for suspicious command execution, and consider network segmentation to reduce exposure.

Recommended fix High confidence

Upgrade to 18.4.6 or later, 19.2.3 or later, 20.1.2 or later, or 20.3.1 or later (recommended: latest stable release in your branch)

  1. 1. Back up the current device configuration using the SD-WAN CLI or vManage backup functionality.
  2. 2. Verify the current running version with the 'show version' command.
  3. 3. Obtain the appropriate software image from Cisco (version 18.4.6 or later, 19.2.3 or later, 20.1.2 or later, or 20.3.1 or later).
  4. 4. Upload the new software image to the device via 'request software' command or via vManage software repository.
  5. 5. Execute 'request software install' to install the new image.
  6. 6. After installation completes, reboot the device with 'request system reboot'.
  7. 7. Verify successful upgrade with 'show version' command confirming the fixed version is running.
Caveat Standard upgrade precautions apply: backup configuration before upgrade, test in lab environment first, review Cisco release notes for your specific version for any configuration or compatibility considerations

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Sd Wan Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,690
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,304.

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-2021-34726 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