CVE-2021-27253
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. Although authentication is required to exploit this vulnerability, the existing authentication mechanism can be bypassed. The specific flaw exists within the handling of the rc_service parameter provided to apply_bind.cgi. The issue results from the lack of proper validation of a user-supplied string before using it to execute a system call. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-12303.
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 analysisData overflows a buffer allocated on the heap, corrupting neighbouring heap structures and allocator metadata that a patient attacker can groom into control of execution. It is subtler than a stack overflow but just as dangerous. The fix is validating lengths before every write and using safe allocators and bounded operations.
General guidance for the heap-based buffer overflow 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
Br200/Br500: Firmware 5.10.0.5 | D7800: Firmware 1.0.1.60 | Ex6100v2/Ex6150: Firmware 1.0.1.98 | Ex6250/Ex6400v2: Firmware 1.0.0.134 | Ex6400: Firmware 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's web management interface by navigating to its IP address (typically 192.168.1.1 or 192.168.0.1)
- 3. Log into the administrator console with credentials that have administrative privileges
- 4. Navigate to the Administration or Settings section, then locate Firmware Update or Router Update option
- 5. Check the current firmware version under the Router Status or Device Information section
- 6. If the current version is below the fixed version for your model, download the latest firmware from the official NETGEAR support site (support.netgear.com) matching your exact model number
- 7. In the firmware update section, either select the downloaded firmware file or enable automatic check for updates
- 8. Wait for the firmware upload and installation to complete - do not power off the device during this process
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-2021-27253 — 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-2021-27253 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
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