CVE-2021-27251
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 · uneditedThis vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR Nighthawk R7800. Authentication is not required to exploit this vulnerability The specific flaw exists within handling of firmware updates. The issue results from a fallback to a insecure protocol to deliver updates. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-12308.
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 analysisSensitive information is transmitted over an unencrypted channel, so anyone positioned on the network path can read it as it passes. Credentials, tokens, and personal data are the usual casualties. The fix is to encrypt everything sensitive in transit with TLS and to remove any plaintext fallback.
General guidance for the cleartext transmission class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →
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< 5.10.0.5< 5.10.0.5< 1.0.1.60< 1.0.1.98< 1.0.1.98< 1.0.0.134< 1.0.2.158< 1.0.0.134CVSS 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
- Adjacent
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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 · scoped1.0.0.1341.0.1.601.0.1.98
Model-specific: Br200/Br500→5.10.0.5 | D7800→1.0.1.60 | Ex6100v2/Ex6150→1.0.1.98 | Ex6250/Ex6400v2→1.0.0.134 | Ex6400→1.0.2.158
- 1. Identify the exact NETGEAR device model from the affected list (Br200, Br500, D7800, Ex6100v2, Ex6150, Ex6250, Ex6400, or Ex6400v2)
- 2. Access the device web interface or admin panel
- 3. Navigate to the Firmware Update or Administration section
- 4. Check current firmware version under the Router Info or Device Info page
- 5. Download the appropriate firmware update from the NETGEAR support site (support.netgear.com) for your specific model
- 6. Upload and apply the firmware update: For Br200/Br500: upgrade to 5.10.0.5 or later | For D7800: upgrade to 1.0.1.60 or later | For Ex6100v2/Ex6150: upgrade to 1.0.1.98 or later | For Ex6250/Ex6400v2: upgrade to 1.0.0.134 or later | For Ex6400: upgrade to 1.0.2.158 or later
- 7. Wait for the firmware upload and installation to complete (do not power off the device)
- 8. After reboot, verify the new firmware version is installed
Generated from the published advisory — verify against the referenced sources before acting.
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Free · runs locallyCheck whether your project pulls in CVE-2021-27251 — 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-2021-27251 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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- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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