CVE-2021-21539
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 · uneditedDell EMC iDRAC9 versions prior to 4.40.00.00 contain a Time-of-check Time-of-use (TOCTOU) race condition vulnerability. A remote authenticated attacker could potentially exploit this vulnerability to gain elevated privileges when a user with higher privileges is simultaneously accessing iDRAC through the web interface.
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 confidenceDell EMC iDRAC9 versions prior to 4.40.00.00 contain a TOCTOU race condition in the web interface. An authenticated attacker with lower privileges can exploit the race between privilege verification and action execution to gain elevated privileges when a higher-privileged user is simultaneously accessing the iDRAC web interface.
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< 4.40.00.00CVSS 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
- Network
- Complexity
- High
- Privileges
- Low
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/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 checksWork through these to decide whether this CVE applies to you.
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Identify iDRAC9 firmware version via web interfaceLog into the iDRAC web UI and navigate to the About page (typically under Maintenance > System Repair and Update or simply /about in the URL). Locate the firmware version field labeled 'iDRAC' or 'Firmware Version'.Affected if The displayed version number is less than 4.40.00.00 (for example, 4.30.10.00, 4.20.00.00, etc.)
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Identify iDRAC9 firmware version via RACADM CLIRun the command 'racadm get iDRAC.FirmwareInfo' or 'racadm fwversion' from a system with RACADM installed and network access to the iDRAC. Locate the 'Firmware Version' or 'Build Version' field in the output.Affected if The reported firmware version is a release prior to 4.40.00.00.
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Identify iDRAC9 firmware version via Redfish APISend a GET request to 'https://<iDRAC-IP>/redfish/v1/Managers/iDRAC.Embedded.1/Attributes' or '/redfish/v1/Managers/System.Embedded.1' and inspect the 'FirmwareVersion' field in the JSON response.Affected if The FirmwareVersion value is lower than 4.40.00.00.
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Verify the iDRAC9 model specificallyConfirm the device is indeed iDRAC9 (not iDRAC8 or iDRAC7) by checking the product name in the web UI About page, via 'racadm get System.Links' or the Redfish /Managers endpoint. The vulnerability applies only to iDRAC9.Affected if The device is iDRAC9 and the firmware version is below 4.40.00.00.
You are affected if your Dell iDRAC9 firmware version is any release prior to 4.40.00.00, as the TOCTOU race condition exists in all earlier versions.
Generated from the published advisory. Verify against your own configuration.
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 data4.40.00.00
Update iDRAC9 firmware to version 4.40.00.00 or later to patch the race condition vulnerability.
- Consultation3.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-21539 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-21539 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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