This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR R6400 and R6700 firmwar…

published 2021-03-29 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-14004

cvss: 8.8; version 3.0, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.8%; EPSS 0.8% chance of exploitation in 30 days, percentile 55%
public exploits: 0; none known

This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR R6400 and R6700 firmware version 1.0.4.98 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the upnpd service, which listens on UDP port 1900 by default. A crafted MX header field in an SSDP message can trigger an overflow of a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-11851.

Patch / fix

fixed in 20

netgear d6220_firmware 1.0.0.68
netgear d6400_firmware 1.0.0.102
netgear d7000_firmware 1.0.0.66
netgear d8500_firmware 1.0.3.60
netgear dc112a_firmware 1.0.0.54
netgear ex7000_firmware 1.0.1.94
netgear ex7500_firmware 1.0.0.72
netgear r6250_firmware 1.0.4.48
netgear r6300_firmware 1.0.4.50
netgear r6400_firmware 1.0.1.68, 1.0.4.102
netgear r6700_firmware 1.0.4.102
netgear r6900p_firmware 1.3.2.132
netgear r7000_firmware 1.0.11.116
netgear r7000p_firmware 1.3.2.132
netgear r7100lg_firmware 1.0.0.64
netgear r7850_firmware 1.0.5.68
netgear r7900_firmware 1.0.4.38
netgear r7900p_firmware 1.4.1.68
netgear r7960p_firmware 1.4.1.68
netgear r8000_firmware 1.0.4.68

Exploit prediction

0.77% chance of exploitation in the next 30 days, higher than 55% of all scored CVEs (FIRST EPSS, 2026-11-08).

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 Multiple Routers

Classification

Weakness

CWE-121 Stack-based Buffer Overflow

References

kb.netgear.com /000062820/Security-Advisory-for-Stack-based-Buffer-Overflow-Remote-Code-Execution-Vulnerability-on-Some-Route
vendor-advisory
zerodayinitiative.com /advisories/ZDI-21-206/
third-party-advisory, vdb-entry

Sources

CVE List CVE-2021-27239
NVD CVE-2021-27239

Fencer Vulns 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.

Summary