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ExploitedNot in CISA KEV yet

CVE-2021-20166

Exploitation confirmed. First attested on 2023-10-14 by GCVE · kevintel, GCVE · shadowserver.

  • Published2021-12-30
  • WeaknessCWE-120

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Netgear RAX43 version 1.0.3.96 contains a buffer overrun vulnerability. The URL parsing functionality in the cgi-bin endpoint of the router containers a buffer overrun issue that can redirection control flow of the applicaiton.

Timeline

dates in UTC
  1. 2021-12-3022:15CVE publishedNVD
  2. 2023-10-1414:56Listed as exploited by GCVEGCVE
  3. 2023-10-1414:56Exploitation first reportedGCVE

Observed activity

isMalicious corpus · updated 2026-11-03 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-20166?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-20166?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Netgear rax43 firmwareversion to verify
BranchAffectedFixed in
1.0= 1.0.3.96no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

No fix published by the sources we read yet. NVD record

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub
Metasploit modules
none listed
Metasploit Framework

Sources

  • GCVEexploitation2023-10-14
  • NVDCVSS 3.18.8read 2026-10-23
  • NVDCVSS 2.05.8read 2026-10-23
  • NVDweakness (CWE)CWE-120read 2026-10-23
  • FIRST EPSSEPSS score2.1 %2026-11-03

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2021-12-30
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

What is CVE-2021-20166?

Netgear RAX43 version 1.0.3.96 contains a buffer overrun vulnerability. The URL parsing functionality in the cgi-bin endpoint of the router containers a buffer overrun issue that can redirection control flow of the applicaiton.

Is CVE-2021-20166 actively exploited?

Active exploitation of CVE-2021-20166 has not been confirmed. Its EPSS score was 2.1% on 2026-11-03, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-20166?

CVE-2021-20166 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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