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CVE-2021-27251

26
FAUCET Score

CVE-2021-27251 is a critical vulnerability affecting NETGEAR Nighthawk R7800 routers, allowing network-adjacent attackers to execute arbitrary code with root privileges. This flaw stems from the device's fallback to an insecure protocol for firmware updates, requiring no authentication for exploitation. With a CVSS score of 8.8 (High), it poses a significant risk due to its low attack complexity and complete compromise potential (Confidentiality, Integrity, Availability). While no public exploit code or active exploitation has been observed, and community discussion is minimal, the inherent risk remains high.

Impacted Technologies

VendorProductVersion(s)CPE
< 5.10.0.5CPE matchmatch criteria
cpe:2.3:o:netgear:br200_firmware:*:*:*:*:*:*:*:*
< 5.10.0.5CPE matchmatch criteria
cpe:2.3:o:netgear:br500_firmware:*:*:*:*:*:*:*:*
< 1.0.1.60CPE matchmatch criteria
cpe:2.3:o:netgear:d7800_firmware:*:*:*:*:*:*:*:*
< 1.0.1.98CPE matchmatch criteria
cpe:2.3:o:netgear:ex6100v2_firmware:*:*:*:*:*:*:*:*
< 1.0.1.98CPE matchmatch criteria
cpe:2.3:o:netgear:ex6150_firmware:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

8.8HIGH

CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
ADJACENT_NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
5.9
CvssVersion
3.0

Exploit Intelligence

EPSS Score
0.73%
Probability of exploitation in next 30 days
EPSS Percentile
50.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0073 is in the 56th percentile among its peer group of 1,875 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.2 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

kb.netgear.com / 000062883/Security-Advisory-for-Multiple-Vulnerabilities-on-Some-Routers-Satellites-and-Extenders
PatchVendor Advisory
zerodayinitiative.com / advisories/ZDI-21-247
Third Party AdvisoryVDB Entry