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CVE-2021-27256

27
FAUCET Score

CVE-2021-27256 is a critical vulnerability affecting NETGEAR R7800 firmware version 1.0.2.76, allowing network-adjacent attackers to execute arbitrary code as root. The flaw stems from improper validation of the 'rc_service' parameter in 'apply_save.cgi', leading to a system call injection. With a CVSS score of 8.8 (High), this vulnerability is easily exploitable over the network without user interaction, despite requiring an authentication bypass. There is currently no public exploit code available, nor any evidence of active exploitation or significant community discussion.

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:ex6150v2_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
0.87%
Probability of exploitation in next 30 days
EPSS Percentile
55.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0087 is in the 68th 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-21-262
Third Party AdvisoryVDB Entry