How severe is CVE-2021-27251?

CVE-2021-27251 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-27251 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (50th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-27251?

CVE-2021-27251 primarily affects Netgear Br200 Firmware. In total, 43 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-27251?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-27251 published?

CVE-2021-27251 was published on 2021-04-14 and last updated on 2026-06-17.

CVE-2021-27251

CVE-2021-27251 is a high-severity vulnerability in Netgear Br200 Firmware with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-319.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v2: 8.3
EPSS exploit prediction: 1% (50th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-319
Affected product: Netgear Br200 Firmware
Published: 2021-04-14
Last modified: 2026-06-17

Description

This 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.

Frequently asked questions

What is CVE-2021-27251?: This 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.
How severe is CVE-2021-27251?: CVE-2021-27251 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-27251 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (50th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-27251?: CVE-2021-27251 primarily affects Netgear Br200 Firmware. In total, 43 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-27251?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-27251 published?: CVE-2021-27251 was published on 2021-04-14 and last updated on 2026-06-17.

References

Affected products (43)

cpe:2.3:o:netgear:br200_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:br500_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:d7800_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:ex6100v2_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:ex6150_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:ex6250_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:ex6400_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:ex6400v2_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:ex6410_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:ex6420_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:ex7300_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:ex7300v2_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:ex7320_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:ex7700_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:ex8000_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:lbr20_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r7800_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r8900_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r9000_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbk12_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbk13_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbk14_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbk15_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbk20_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbk23_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbk40_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbk43_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbk43s_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbk44_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbk50_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbk53_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbr10_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbr20_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbr40_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbr50_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbs10_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbs20_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbs40_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbs50_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:rbs50y_firmware:*:*:*:*:*:*:*:*

More vulnerabilities in Netgear Br200 Firmware

CVE-2021-27253 — High (CVSS 8.8): This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR…
CVE-2021-27252 — High (CVSS 8.8): This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR…
CVE-2021-27256 — High (CVSS 8.8): This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR…
CVE-2021-27255 — High (CVSS 8.8): This vulnerability allows remote attackers to execute arbitrary code on affected installations of NETGEAR R7800…
CVE-2021-27254 — High (CVSS 8.8): This vulnerability allows network-adjacent attackers to bypass authentication on affected installations of NETGEAR…
CVE-2021-27257 — Medium (CVSS 6.5): This vulnerability allows network-adjacent attackers to compromise the integrity of downloaded information on affected…

All CVEs affecting Netgear Br200 Firmware →

Other CWE-319 (Cleartext Transmission of Sensitive Information) vulnerabilities

CVE-2025-4378 — Critical (CVSS 10.0): Cleartext Transmission of Sensitive Information, Use of Hard-coded Credentials vulnerability in Ataturk University…
CVE-2025-47419 — Critical (CVSS 10.0): Cleartext Transmission of Sensitive Information vulnerability in Crestron Automate VX allows Sniffing Network…
CVE-2026-48902 — Critical (CVSS 9.8): The password and username reset features created plain http links for https connections if the "Force SSL" flag wasn't…
CVE-2025-34271 — Critical (CVSS 9.8): Nagios Log Server versions prior to 2024R2.0.2 contain a vulnerability in the cluster manager component when…
CVE-2025-32880 — Critical (CVSS 9.8): An issue was discovered on COROS PACE 3 devices through 3.0808.0. It implements a function to connect the watch to a…
CVE-2025-26199 — Critical (CVSS 9.8): CloudClassroom-PHP-Project v1.0 is affected by an insecure credential transmission vulnerability. The application…

Browse all CWE-319 (Cleartext Transmission of Sensitive Information) vulnerabilities →