CVE-2021-21540
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 stack-based overflow vulnerability. A remote authenticated attacker could potentially exploit this vulnerability to overwrite configuration information by injecting arbitrarily large payload.
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 stack-based buffer overflow vulnerability. A remote authenticated attacker can inject an arbitrarily large payload to overwrite iDRAC configuration information, potentially gaining further control over the baseboard management controller.
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
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/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 checksWork through these to decide whether this CVE applies to you.
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Locate iDRAC9 firmware version in web interfaceLog into the iDRAC web interface, navigate to Overview > iDRAC Settings > Lifecycle Controller, and locate the firmware version displayed under the iDRAC firmware sectionAffected if The displayed version is less than 4.40.00.00
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Query iDRAC firmware version via Redfish APISend a GET request to https://<idrac-ip>/redfish/v1/Managers/iDRAC.Embedded.1/Attributes and examine the 'IdracDevBios' or 'LifecycleController' firmware version attributes in the JSON responseAffected if The firmware version returned is less than 4.40.00.00
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Query iDRAC firmware version via IPMIRun the command 'ipmitool -I lanplus -H <idrac-ip> -U <username> -P <password> fru print 0' or 'ipmitool -I lanplus -H <idrac-ip> -U <username> -P <password> mc info' to retrieve the iDRAC firmware version from the Field Replaceable Unit or Management Controller informationAffected if The firmware version shown is less than 4.40.00.00
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Check firmware version via racadm CLI toolUse the Dell racadm utility: 'racadm -r <idrac-ip> -u <username> -p <password> get idrac.firmware' to retrieve the current iDRAC firmware build versionAffected if The reported firmware version is below 4.40.00.00
Your iDRAC9 is affected if the installed firmware version is any build earlier than 4.40.00.00, as the stack-based buffer overflow vulnerability exists in all prior 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
Upgrade iDRAC9 firmware to version 4.40.00.00 or later to remediate this vulnerability.
- Consultation2.0 h
- Implementation1.0 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-2021-21540 — 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-2021-21540 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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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.
- 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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