HOMEVULNERABILITIESCVE-2021-34991
HIGH

CVE-2021-34991

CWE-121Published: November 15, 2021· Updated: Jun 17, 2026

8.8
CVSS v3.1

Official 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.

NVD Source

Technical Analysis

CVE-2021-34991 requires adjacent network access, limiting remote exploitation but still posing risk in shared or local network environments.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 8.8.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorAdjacent
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

netgear88 product(s)
ex3700 firmwareex3700ex3800 firmwareex3800ex6120 firmwareex6120ex6130 firmwareex6130r6400 firmwarer6400r6400v2 firmwarer6400v2+76
Source: NVD CPE · 88 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttps://kb.netgear.com/000064361/Security-Advisory-for-Pre-Authentication-Buffer-Overflow-on-Multiple-Products-PSV-2021-0168
ADVISORYhttps://www.zerodayinitiative.com/advisories/ZDI-21-1303/
ADVISORYhttps://kb.netgear.com/000064361/Security-Advisory-for-Pre-Authentication-Buffer-Overflow-on-Multiple-Products-PSV-2021-0168
ADVISORYhttps://www.zerodayinitiative.com/advisories/ZDI-21-1303/

All References (4)

→
https://kb.netgear.com/000064361/Security-Advisory-for-Pre-Authentication-Buffer-Overflow-on-Multiple-Products-PSV-2021-0168Vendor Advisory
→
https://www.zerodayinitiative.com/advisories/ZDI-21-1303/Third Party Advisory · VDB Entry
→
https://kb.netgear.com/000064361/Security-Advisory-for-Pre-Authentication-Buffer-Overflow-on-Multiple-Products-PSV-2021-0168Vendor Advisory
→
https://www.zerodayinitiative.com/advisories/ZDI-21-1303/Third Party Advisory · VDB Entry

Quick Facts

CVE IDCVE-2021-34991
CVSS Score8.8 / 10
SeverityHIGH
WeaknessCWE-121
CISA KEVNo
Affected1 vendor(s)
PublishedNov 15, 2021

Related CVEs (CWE-121)

CVE-2014-0787
10.0
CVE-2021-21961
10.0
CVE-2020-14498
10.0
CVE-2023-3943
10.0
CVE-2021-21960
10.0
CVE-2026-12848
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-34991 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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