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Firepower Management Center Virtual ApplianceApplication · Cisco

CVE-2021-34761

MEDIUM · 6.0 CVSS v3.1 Published 2021-10-27
Fix available
A fix is available. Upgrade to 6.4.0.13 / 6.6.5 or later.
See remediation →
62/100
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 Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, local attacker to overwrite or append arbitrary data to system files using root-level privileges. The attacker must have administrative credentials on the device. This vulnerability is due to incomplete validation of user input for a specific CLI command. An attacker could exploit this vulnerability by authenticating to the device with administrative privileges and issuing a CLI command with crafted user parameters. A successful exploit could allow the attacker to overwrite or append arbitrary data to system files using 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 local authenticated attacker with administrative credentials on Cisco FTD can exploit incomplete input validation in a specific CLI command to write arbitrary data to system files with root-level privileges, achieving local privilege escalation.

MitigationApply the Cisco security patch for this vulnerability and ensure administrative CLI access is restricted to trusted, need-to-know personnel.

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
Firepower Management Center Virtual ApplianceApplication
Affected:= 6.2.3= 6.4.0= 6.6.1= 6.7.0= 7.0.0= 7.1.0
Secure Firewall Threat DefenseApplication
Affected:>= 6.4.0, < 6.4.0.13>= 6.6.0, < 6.6.5>= 6.7.0, < 6.7.0.3>= 7.0.0, < 7.0.1
Sourcefire Defense CenterApplication
Affected:= 6.2.3= 6.4.0= 6.6.1= 6.7.0= 7.0.0= 7.1.0

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
None
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/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 Cisco product type
    Run 'show version' or check the system UI to determine if the device is Firepower Management Center Virtual Appliance, Firepower Threat Defense, or Sourcefire Defense Center
    Affected if The device is any of these three product types
  2. Check the installed software version
    Execute 'show version' on the CLI or check the web interface under System > About to obtain the exact version number
    Affected if Version matches: FMC Virtual Appliance = 6.2.3, 6.4.0, 6.6.1, 6.7.0, 7.0.0, or 7.1.0; FTD >= 6.4.0 and < 6.4.0.13, >= 6.6.0 and < 6.6.5, >= 6.7.0 and < 6.7.0.3, or >= 7.0.0 and < 7.0.1; Sourcefire Defense Center = 6.2.3, 6.4.0, 6.6.1, 6.7.0, 7.0.0, or 7.1.0
  3. Verify administrative CLI access is configured
    Check if the device has administrative users with CLI access enabled by reviewing user accounts under 'configure user' or through the web UI under System > Administration > User Management
    Affected if Administrative users exist with CLI access privileges
  4. Confirm the device is reachable via CLI
    Attempt to access the device console or SSH with administrative credentials to confirm CLI access is available
    Affected if CLI access with administrative credentials is possible

A user is affected if they are running an affected product type with a version in the listed vulnerable ranges and administrative CLI access is enabled on the device.

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 6.4.0.13 / 6.6.5 / 6.7.0.3 or later
Fixed in 6.4.0.136.6.56.7.0.3
Interim mitigation

Apply the Cisco security patch for this vulnerability and ensure administrative CLI access is restricted to trusted, need-to-know personnel.

Recommended fix High confidence

Firepower Threat Defense: 6.4.0.13, 6.6.5, 6.7.0.3, or 7.0.1 (depending on current branch) | Firepower Management Center: 6.7.0.3 or 7.0.1 | Sourcefire Defense Center: 6.7.0.3 or 7.0.1

  1. 1. Identify the current version of Cisco FTD or FMC by running 'show version' in the CLI
  2. 2. For Firepower Management Center Virtual Appliance: Upgrade to version 6.7.0.3 or later (or 7.0.1 or later)
  3. 3. For Firepower Threat Defense: Based on your current version branch, upgrade to the appropriate fixed release: 6.4.0.13 or later, 6.6.5 or later, 6.7.0.3 or later, or 7.0.1 or later
  4. 4. For Sourcefire Defense Center: Upgrade to version 6.7.0.3 or later (or 7.0.1 or later)
  5. 5. Download the upgrade image from Cisco (requires valid Cisco.com account)
  6. 6. Follow Cisco's standard upgrade procedure: upload the upgrade package, verify integrity, and apply the upgrade
  7. 7. After upgrade, verify the version with 'show version' and confirm the vulnerability is resolved
Caveat Review Cisco release notes for your specific upgrade path as there may be compatibility considerations and potential impact on existing configurations or integrations

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

Fix this in Firepower Management Center Virtual Appliance Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,840
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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-2021-34761 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