How severe is CVE-2020-27866?

CVE-2020-27866 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-2020-27866 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 9% (94th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-27866?

CVE-2020-27866 primarily affects Netgear Ac2100 Firmware. In total, 19 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-27866?

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-2020-27866 published?

CVE-2020-27866 was published on 2021-02-12 and last updated on 2026-06-17.

CVE-2020-27866

CVE-2020-27866 is a high-severity vulnerability in Netgear Ac2100 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-287.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v2: 8.3
EPSS exploit prediction: 9% (94th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-287
Affected product: Netgear Ac2100 Firmware
Published: 2021-02-12
Last modified: 2026-06-17

Description

This vulnerability allows network-adjacent attackers to bypass authentication on affected installations of NETGEAR R6020, R6080, R6120, R6220, R6260, R6700v2, R6800, R6900v2, R7450, JNR3210, WNR2020, Nighthawk AC2100, and Nighthawk AC2400 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the mini_httpd service, which listens on TCP port 80 by default. The issue results from incorrect string matching logic when accessing protected pages. An attacker can leverage this in conjunction with other vulnerabilities to execute code in the context of root. Was ZDI-CAN-11355.

Frequently asked questions

What is CVE-2020-27866?: This vulnerability allows network-adjacent attackers to bypass authentication on affected installations of NETGEAR R6020, R6080, R6120, R6220, R6260, R6700v2, R6800, R6900v2, R7450, JNR3210, WNR2020, Nighthawk AC2100, and Nighthawk AC2400 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the mini_httpd service, which listens on TCP port 80 by default. The issue results from incorrect string matching logic when accessing protected pages. An attacker can leverage this in conjunction with other vulnerabilities to execute code in the context of root. Was ZDI-CAN-11355.
How severe is CVE-2020-27866?: CVE-2020-27866 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-2020-27866 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 9% (94th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-27866?: CVE-2020-27866 primarily affects Netgear Ac2100 Firmware. In total, 19 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-27866?: 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-2020-27866 published?: CVE-2020-27866 was published on 2021-02-12 and last updated on 2026-06-17.

References

Affected products (19)

cpe:2.3:o:netgear:ac2100_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:ac2400_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:ac2600_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r6700_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r6800_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r6900_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r7200_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r7350_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r7400_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r7450_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r6220_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r6230_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r6260_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r6330_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r6350_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r6850_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r6120_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r6020_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r6080_firmware:*:*:*:*:*:*:*:*

More vulnerabilities in Netgear Ac2100 Firmware

CVE-2021-38516 — Critical (CVSS 10.0): Certain NETGEAR devices are affected by lack of access control at the function level. This affects D6220 before…
CVE-2021-29068 — Critical (CVSS 9.9): Certain NETGEAR devices are affected by a buffer overflow by an authenticated user. This affects R6700v3 before…
CVE-2020-35795 — Critical (CVSS 9.8): Certain NETGEAR devices are affected by a buffer overflow by an unauthenticated attacker. This affects AC2100 before…
CVE-2020-35800 — Critical (CVSS 9.4): Certain NETGEAR devices are affected by incorrect configuration of security settings. This affects AC2100 before…
CVE-2020-26927 — Critical (CVSS 9.4): Certain NETGEAR devices are affected by authentication bypass. This affects D6200 before 1.1.00.40, D7000 before…
CVE-2021-34865 — High (CVSS 8.8): This vulnerability allows network-adjacent attackers to bypass authentication on affected installations of multiple…

All CVEs affecting Netgear Ac2100 Firmware →

Other CWE-287 (Improper Authentication) vulnerabilities

CVE-2026-45480 — Critical (CVSS 10.0): Improper authentication in Azure Active Directory allows an unauthorized attacker to elevate privileges over a network.
CVE-2026-46389 — Critical (CVSS 10.0): UDS Identity Config builds the Keycloak configuration image (realm, plugins, theme, truststore, JARs) consumed by UDS…
CVE-2026-10611 — Critical (CVSS 10.0): An authentication bypass vulnerability exists in MISP when LDAP mixed authentication is enabled with OTP enforcement.…
CVE-2026-47280 — Critical (CVSS 10.0): Improper authentication in Azure Resource Manager (ARM) allows an unauthorized attacker to elevate privileges over a…
CVE-2026-42822 — Critical (CVSS 10.0): Improper authentication in Azure Local Disconnected Operations allows an unauthorized attacker to elevate privileges…
CVE-2026-20182 — Critical (CVSS 10.0): May 2026: This security advisory provides the details and fix information for a vulnerability that was discovered and…

Browse all CWE-287 (Improper Authentication) vulnerabilities →