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.

Published: 2021-11-15 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-34991 is rated High Risk (72.4/100): CVSS High severity, with high exploitation likelihood (EPSS 5.67%, 92th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. EPSS rose +5.38% over the last day, indicating growing attacker interest. High exploitation likelihood—assess exposure and prioritize remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-34991

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.29% 5.67% +5.38%
2 2026-04-08 0.21% 0.29% +0.08%
3 2026-02-10 — 0.21% —

Full EPSS history (19 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-34991

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.8 3.1 HIGH
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:A)
Attacker has to be nearby on the network—same office, same link, that vibe—not the whole wide internet.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]
8.8 3.0 HIGH
CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:A)
Attacker has to be nearby on the network—same office, same link, that vibe—not the whole wide internet.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]
8.3 2.0 HIGH
AV:A/AC:L/Au:N/C:C/I:C/A:C Click to expand
Access vector (AV:A)
Requires access to an adjacent network segment.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:C)
Complete confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
 6.5 10.0 [email protected]

Weakness enumeration for CVE-2021-34991

Affected software / configurations for CVE-2021-34991

Vendor Product Version Raw CPE
netgear ex3700_firmware < 1.0.0.94 cpe:2.3:o:netgear:ex3700_firmware:*:*:*:*:*:*:*:*
netgear ex3800_firmware < 1.0.0.94 cpe:2.3:o:netgear:ex3800_firmware:*:*:*:*:*:*:*:*
netgear ex6120_firmware < 1.0.0.66 cpe:2.3:o:netgear:ex6120_firmware:*:*:*:*:*:*:*:*
netgear ex6130_firmware < 1.0.0.66 cpe:2.3:o:netgear:ex6130_firmware:*:*:*:*:*:*:*:*
netgear r6400_firmware < 1.0.1.76 cpe:2.3:o:netgear:r6400_firmware:*:*:*:*:*:*:*:*
netgear r6400v2_firmware < 1.0.4.120 cpe:2.3:o:netgear:r6400v2_firmware:*:*:*:*:*:*:*:*
netgear r6700v3_firmware < 1.0.4.120 cpe:2.3:o:netgear:r6700v3_firmware:*:*:*:*:*:*:*:*
netgear r6900p_firmware < 1.3.3.142 cpe:2.3:o:netgear:r6900p_firmware:*:*:*:*:*:*:*:*
netgear r7000_firmware < 1.0.11.128 cpe:2.3:o:netgear:r7000_firmware:*:*:*:*:*:*:*:*
netgear r7000p_firmware < 1.3.3.142 cpe:2.3:o:netgear:r7000p_firmware:*:*:*:*:*:*:*:*
netgear r7100lg_firmware < 1.0.0.72 cpe:2.3:o:netgear:r7100lg_firmware:*:*:*:*:*:*:*:*
netgear r7850_firmware < 1.0.5.76 cpe:2.3:o:netgear:r7850_firmware:*:*:*:*:*:*:*:*
netgear r7900p_firmware < 1.4.2.84 cpe:2.3:o:netgear:r7900p_firmware:*:*:*:*:*:*:*:*
netgear r7960p_firmware < 1.4.2.84 cpe:2.3:o:netgear:r7960p_firmware:*:*:*:*:*:*:*:*
netgear r8000_firmware < 1.0.4.76 cpe:2.3:o:netgear:r8000_firmware:*:*:*:*:*:*:*:*
netgear r8000p_firmware < 1.4.2.84 cpe:2.3:o:netgear:r8000p_firmware:*:*:*:*:*:*:*:*
netgear r8300_firmware < 1.0.2.156 cpe:2.3:o:netgear:r8300_firmware:*:*:*:*:*:*:*:*
netgear r8500_firmware < 1.0.2.156 cpe:2.3:o:netgear:r8500_firmware:*:*:*:*:*:*:*:*
netgear rax15_firmware < 1.0.4.100 cpe:2.3:o:netgear:rax15_firmware:*:*:*:*:*:*:*:*
netgear rax20_firmware < 1.0.4.100 cpe:2.3:o:netgear:rax20_firmware:*:*:*:*:*:*:*:*
netgear rax200_firmware < 1.0.5.132 cpe:2.3:o:netgear:rax200_firmware:*:*:*:*:*:*:*:*
netgear rax35v2_firmware < 1.0.4.100 cpe:2.3:o:netgear:rax35v2_firmware:*:*:*:*:*:*:*:*
netgear rax38v2_firmware < 1.0.4.100 cpe:2.3:o:netgear:rax38v2_firmware:*:*:*:*:*:*:*:*
netgear rax40v2_firmware < 1.0.4.100 cpe:2.3:o:netgear:rax40v2_firmware:*:*:*:*:*:*:*:*
netgear rax42_firmware < 1.0.4.100 cpe:2.3:o:netgear:rax42_firmware:*:*:*:*:*:*:*:*
netgear rax43_firmware < 1.0.4.100 cpe:2.3:o:netgear:rax43_firmware:*:*:*:*:*:*:*:*
netgear rax45_firmware < 1.0.4.100 cpe:2.3:o:netgear:rax45_firmware:*:*:*:*:*:*:*:*
netgear rax48_firmware < 1.0.4.100 cpe:2.3:o:netgear:rax48_firmware:*:*:*:*:*:*:*:*
netgear rax50_firmware < 1.0.4.100 cpe:2.3:o:netgear:rax50_firmware:*:*:*:*:*:*:*:*
netgear rax50s_firmware < 1.0.4.100 cpe:2.3:o:netgear:rax50s_firmware:*:*:*:*:*:*:*:*
netgear rax75_firmware < 1.0.5.132 cpe:2.3:o:netgear:rax75_firmware:*:*:*:*:*:*:*:*
netgear rax80_firmware < 1.0.5.132 cpe:2.3:o:netgear:rax80_firmware:*:*:*:*:*:*:*:*
netgear raxe450_firmware < 1.0.8.70 cpe:2.3:o:netgear:raxe450_firmware:*:*:*:*:*:*:*:*
netgear raxe500_firmware < 1.0.8.70 cpe:2.3:o:netgear:raxe500_firmware:*:*:*:*:*:*:*:*
netgear rs400_firmware < 1.5.1.80 cpe:2.3:o:netgear:rs400_firmware:*:*:*:*:*:*:*:*
netgear wndr3400v3_firmware < 1.0.1.42 cpe:2.3:o:netgear:wndr3400v3_firmware:*:*:*:*:*:*:*:*
netgear wnr3500lv2_firmware < 1.2.0.70 cpe:2.3:o:netgear:wnr3500lv2_firmware:*:*:*:*:*:*:*:*
netgear xr300_firmware < 1.0.3.68 cpe:2.3:o:netgear:xr300_firmware:*:*:*:*:*:*:*:*
netgear d6220_firmware < 1.0.0.76 cpe:2.3:o:netgear:d6220_firmware:*:*:*:*:*:*:*:*
netgear d6400_firmware < 1.0.0.108 cpe:2.3:o:netgear:d6400_firmware:*:*:*:*:*:*:*:*
netgear d7000v2_firmware < 1.0.0.76 cpe:2.3:o:netgear:d7000v2_firmware:*:*:*:*:*:*:*:*
netgear dgn2200v4_firmware < 1.0.0.126 cpe:2.3:o:netgear:dgn2200v4_firmware:*:*:*:*:*:*:*:*
netgear dc112a_firmware < 1.0.0.62 cpe:2.3:o:netgear:dc112a_firmware:*:*:*:*:*:*:*:*
netgear cax80_firmware < 2.1.3.5 cpe:2.3:o:netgear:cax80_firmware:*:*:*:*:*:*:*:*

References for CVE-2021-34991

cvelogic Threat Intelligence