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CVE-2020-27866: This vulnerability allows network-adjacent attackers to bypass authentication on affected installations of NET

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HIGH 8.8UPGRADEUPGRADEUPGRADE

CVE-2020-27866 is a high-severity flaw (CVSS 8.8) affecting ac2100 firmware, ac2400 firmware, ac2600 firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 mat

Why this priority

  • High severity
  • EPSS top 5%: very likely to be exploited

A fixed release or distro patch exists.

Risk facts

CVSS score8.8 (High)
Attack vectorAdjacent network
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance8.7% (top 5%)
CISA exploited listNo
WeaknessCWE-288, CWE-287
Published2021-02-12
Last modified2026-06-17
Publisher (CNA): Zero Day Initiative · Vendor: netgear

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Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

netgear ac2100 firmware UPGRADE
Affected: < 1.2.0.76
Fixed in: 1.2.0.76
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
netgear ac2400 firmware UPGRADE
Affected: < 1.2.0.76
Fixed in: 1.2.0.76
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
netgear ac2600 firmware UPGRADE
Affected: < 1.2.0.76
Fixed in: 1.2.0.76
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
netgear r6700 firmware UPGRADE
Affected: < 1.2.0.76
Fixed in: 1.2.0.76
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
netgear r6800 firmware UPGRADE
Affected: < 1.2.0.76
Fixed in: 1.2.0.76
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
netgear r6900 firmware UPGRADE
Affected: < 1.2.0.76
Fixed in: 1.2.0.76
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-27866?

ac2100 firmware: upgrade to 1.2.0.76; ac2400 firmware: upgrade to 1.2.0.76; ac2600 firmware: upgrade to 1.2.0.76. Exact commands for each OS are on this page.

Is CVE-2020-27866 being exploited?

CVE-2020-27866 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-27866 affect?

CVE-2020-27866 affects ac2100 firmware, ac2400 firmware, ac2600 firmware. Severity is high (CVSS 8.8). 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 r

How urgent is CVE-2020-27866?

Priority 55/100. High severity; EPSS top 5%: very likely to be exploited

Software pages

Apache HTTP Server vulnerabilities · Netgear vulnerabilities

Related CVEs

References

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