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Fencer Intel
high 8.8

CVE-2021-34991 json

This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR R6400v2 1.0.4.106_10.0.…

published 4y ago modified 4mo ago also EUVD-2021-21638

cvss
8.8
version 3.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
5.7%
EPSS 5.7% chance of exploitation in 30 days, percentile 93%
public exploits
0
none known

Summary

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.

Patch / fix

  • netgear ex3700_firmware 1.0.0.94
  • netgear ex3800_firmware 1.0.0.94
  • netgear ex6120_firmware 1.0.0.66
  • netgear ex6130_firmware 1.0.0.66
  • netgear r6400_firmware 1.0.1.76
  • netgear r6400v2_firmware 1.0.4.120
  • netgear r6700v3_firmware 1.0.4.120
  • netgear r6900p_firmware 1.3.3.142
  • netgear r7000_firmware 1.0.11.128
  • netgear r7000p_firmware 1.3.3.142
  • netgear r7100lg_firmware 1.0.0.72
  • netgear r7850_firmware 1.0.5.76
  • netgear r7900p_firmware 1.4.2.84
  • netgear r7960p_firmware 1.4.2.84
  • netgear r8000_firmware 1.0.4.76
  • netgear r8000p_firmware 1.4.2.84
  • netgear r8300_firmware 1.0.2.156
  • netgear r8500_firmware 1.0.2.156
  • netgear rax15_firmware 1.0.4.100
  • netgear rax20_firmware 1.0.4.100

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Exploit prediction

5.71% chance of exploitation in the next 30 days, higher than 93% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.0 8.8 CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 8.8 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 8.3 AV:A/AC:L/Au:N/C:C/I:C/A:C

Affected products

  • NETGEAR R6400v2

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.