dbcve.org
Fabric Operating SystemOperating system · Broadcom

CVE-2021-27794

HIGH · 7.8 CVSS v3.1 Published 2021-08-12
Fix available
A fix is available. Upgrade to 7.4.2h / 8.2.3a or later.
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 authentication mechanism of Brocade Fabric OS versions before Brocade Fabric OS v.9.0.1a, v8.2.3a and v7.4.2h could allow a user to Login with empty password, and invalid password through telnet, ssh and REST.

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

Brocade Fabric OS contains an authentication bypass vulnerability where users can successfully login using an empty password or invalid password through telnet, SSH, and REST API endpoints. This affects multiple versions prior to the patched releases.

MitigationUpgrade Brocade Fabric OS to version 9.0.1a, 8.2.3a, or 7.4.2h (depending on your release train) to remediate the authentication bypass. Also disable telnet if not required and enforce SSH key-based authentication.

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
Fabric Operating SystemOperating system
Affected:< 7.4.2h>= 8.0.0, < 8.2.3a>= 9.0.0, < 9.0.1a

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. Determine Fabric OS version
    Run the 'version' command on the Fabric OS CLI to obtain the installed version number
    Affected if The version displayed is earlier than 7.4.2h, or falls between 8.0.0 and 8.2.3a, or falls between 9.0.0 and 9.0.1a
  2. Check if telnet service is enabled
    Run 'telnetstat' or check the configuration via 'adminShow' to see if telnet access is permitted
    Affected if Telnet is enabled and the Fabric OS version is in the affected ranges
  3. Check if SSH service is enabled
    Run 'sshStat' or 'sshUtil show' to determine if SSH is active and which authentication methods are permitted
    Affected if SSH is enabled and the Fabric OS version is in the affected ranges
  4. Check if REST API endpoints are accessible
    Attempt a curl or HTTP request to the device's REST API port (typically 8080 or 8443) using an invalid or empty password to test authentication
    Affected if REST API responds to authentication requests and the Fabric OS version is in the affected ranges

A system is affected if it runs Fabric OS version 7.4.2h之前的版本, 8.0.0-8.2.3a之间的版本, 或 9.0.0-9.0.1a之间的版本, and has telnet, SSH, or REST API services 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 7.4.2h / 8.2.3a / 9.0.1a or later
Fixed in 7.4.2h8.2.3a9.0.1a
Interim mitigation

Upgrade Brocade Fabric OS to version 9.0.1a, 8.2.3a, or 7.4.2h (depending on your release train) to remediate the authentication bypass. Also disable telnet if not required and enforce SSH key-based authentication.

Recommended fix High confidence

Upgrade to Fabric OS 7.4.2h, 8.2.3a, or 9.0.1a depending on current version branch (9.0.1a is the latest stable release)

  1. Identify the current Fabric OS version by running 'version' or 'firmwareshow' command
  2. Determine which upgrade path applies based on current version: if < 7.4.2, upgrade to 7.4.2h; if >= 8.0.0 and < 8.2.3, upgrade to 8.2.3a; if >= 9.0.0, upgrade to 9.0.1a
  3. Download the appropriate Fabric OS firmware from Broadcom support portal (support.broadcom.com)
  4. Upload the firmware to the Fabric OS device using 'firmwaredownload' command or management interface
  5. Follow standard Fabric OS upgrade procedure: verify firmware integrity, schedule maintenance window, execute upgrade, and confirm successful completion
  6. After upgrade, verify the fix by confirming version number matches the fixed release
  7. Test authentication via SSH, telnet, and REST API with both valid and invalid credentials to confirm the vulnerability is remediated
Caveat Review Brocade Fabric OS release notes for the target version to check for any configuration or feature changes that may affect existing setup

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

Fix this in Fabric Operating System Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing5.0 h
  • Review / QA3.0 h
17.0 hours of engineering $2,970
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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-2021-27794 in production — separate from our analysis above.

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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