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CVE-2021-27239

26
FAUCET Score

CVE-2021-27239 is a critical stack-based buffer overflow vulnerability affecting NETGEAR R6400 and R6700 routers running firmware version 1.0.4.98. This flaw resides in the upnpd service, allowing unauthenticated, network-adjacent attackers to execute arbitrary code with root privileges by sending a specially crafted SSDP message. With a CVSS score of 8.8 (HIGH), the vulnerability presents a significant risk due to its low attack complexity and complete compromise potential. While no public exploit code or active exploitation has been observed, and community discussion is minimal, the high severity warrants immediate patching for affected devices.

Impacted Technologies

VendorProductVersion(s)CPE
< 1.0.0.68CPE matchmatch criteria
cpe:2.3:o:netgear:d6220_firmware:*:*:*:*:*:*:*:*
< 1.0.0.102CPE matchmatch criteria
cpe:2.3:o:netgear:d6400_firmware:*:*:*:*:*:*:*:*
< 1.0.0.66CPE matchmatch criteria
cpe:2.3:o:netgear:d7000_firmware:*:*:*:*:*:*:*:*
< 1.0.3.60CPE matchmatch criteria
cpe:2.3:o:netgear:d8500_firmware:*:*:*:*:*:*:*:*
< 1.0.0.54CPE matchmatch criteria
cpe:2.3:o:netgear:dc112a_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
0.75%
Probability of exploitation in next 30 days
EPSS Percentile
51.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0075 is in the 57th 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 / 000062820/Security-Advisory-for-Stack-based-Buffer-Overflow-Remote-Code-Execution-Vulnerability-on-Some-Routers-PSV-2020-0432
Vendor Advisory
zerodayinitiative.com / advisories/ZDI-21-206
Third Party AdvisoryVDB Entry