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No exploitation reportedFix available

CVE-2021-34991

No exploitation reported by the sources we read.

  • Published2021-11-15
  • Fixed in2.1.3.5
  • WeaknessCWE-121 · CWE-787

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

This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR R6400v2 1.0.4.106_10.0.80 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the UPnP service, which listens on TCP port 5000 by default. When parsing the uuid request header, the process does not properly validate the length of user-supplied data prior to copying it to a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-14110.

Timeline

dates in UTC
  1. 2021-11-1516:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 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-2021-34991?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-34991?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Netgear cax80 firmwareversion to verify
BranchAffectedFixed in
2.1< 2.1.3.52.1.3.5
Netgear d6220 firmwareversion to verify
BranchAffectedFixed in
1.0< 1.0.0.761.0.0.76
Netgear d6400 firmwareversion to verify
BranchAffectedFixed in
1.0< 1.0.0.1081.0.0.108

41 more products in the sources.

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

Fix

  1. Update Netgear cax80 firmware to 2.1.3.5

Advisories and patches

Detection

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

Sources

  • NVDCVSS 3.18.8read 2026-10-23
  • CNACVSS 3.08.8read 2026-10-23
  • NVDCVSS 2.08.3read 2026-10-23
  • CNAweakness (CWE)CWE-121read 2026-10-23
  • NVDweakness (CWE)CWE-787read 2026-10-23
  • FIRST EPSSEPSS score5.7 %2026-10-22

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
2021-11-15
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

What is CVE-2021-34991?

This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR R6400v2 1.0.4.106_10.0.80 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the UPnP service, which listens on TCP port 5000 by default. When parsing the uuid request header, the process does not properly validate the length of user-supplied data prior to copying it to a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-14110.

Is CVE-2021-34991 actively exploited?

Active exploitation of CVE-2021-34991 has not been confirmed. Its EPSS score was 5.7% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-34991?

CVE-2021-34991 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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