CVE-2018-21156 [High] | Memory Corruption in D6220 Firmware

Certain NETGEAR devices are affected by a buffer overflow by an authenticated user. This affects D6220 before 1.0.0.38, D6400 before 1.0.0.74, D7000v2 before 1.0.0.74, D8500 before 1.0.3.39, DGN2200v4 before 1.0.0.102, DGN2200Bv4 before 1.0.0.102, EX3700 before 1.0.0.70, EX3800 before 1.0.0.70, EX6000 before 1.0.0.30, EX6100 before 1.0.2.22, EX6120 before 1.0.0.40, EX6130 before 1.0.0.22, EX6150 before 1.0.0.38, EX6200 before 1.0.3.86, EX7000 before 1.0.0.64, R6250 before 1.0.4.20, R6300v2 before 1.0.4.22, R6400 before 1.0.1.32, R6400v2 before 1.0.2.52, R6700 before 1.0.1.44, R6900 before 1.0.1.44, R6900P before 1.3.0.18, R7000 before 1.0.9.28, R7000P before 1.3.0.18, R7300DST before 1.0.0.62, R7900 before 1.0.2.10, R7900P before 1.3.0.10, R8000 before 1.0.4.12, R8000P before 1.3.0.10, R8300 before 1.0.2.116, R8500 before 1.0.2.116, WN2500RPv2 before 1.0.1.52, WNDR3400v3 before 1.0.1.18, and WNR3500Lv2 before 1.2.0.46.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.33%	1.35%	+1.02%
2	2025-03-30	0.69%	0.33%	-0.36%
3	2025-03-29	—	0.69%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.33%

1.35%

+1.02%

2025-03-30

0.69%

0.33%

-0.36%

2025-03-29

—

0.69%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.2	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. 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:H) They need powerful rights—admin, root, or similar—before this pays off. 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.	1.2	5.9	[email protected]
6.8	3.0	MEDIUM	`CVSS:3.0/AV:A/AC:L/PR:H/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:H) They need powerful rights—admin, root, or similar—before this pays off. 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.	0.9	5.9	[email protected]
6.5	2.0	MEDIUM	`AV:N/AC:L/Au:S/C:P/I:P/A:P` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:S) A single authentication is required. Confidentiality impact (C:P) Partial confidentiality impact. Integrity impact (I:P) Partial integrity impact. Availability impact (A:P) Partial availability impact.	8.0	6.4	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.2

3.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
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:H): They need powerful rights—admin, root, or similar—before this pays off.
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.

1.2

5.9

[email protected]

6.8

3.0

MEDIUM

CVSS:3.0/AV:A/AC:L/PR:H/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:H): They need powerful rights—admin, root, or similar—before this pays off.
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.

0.9

5.9

[email protected]

6.5

2.0

MEDIUM

AV:N/AC:L/Au:S/C:P/I:P/A:P Click to expand

Access vector (AV:N): Can be exploited remotely over network reachability.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:S): A single authentication is required.
Confidentiality impact (C:P): Partial confidentiality impact.
Integrity impact (I:P): Partial integrity impact.
Availability impact (A:P): Partial availability impact.

8.0

6.4

[email protected]

Affected software / configurations for CVE-2018-21156

Vendor	Product	Version	Raw CPE
netgear	d6220_firmware	< 1.0.0.38	cpe:2.3:o:netgear:d6220_firmware::::::::
netgear	d6400_firmware	< 1.0.0.74	cpe:2.3:o:netgear:d6400_firmware::::::::
netgear	d7000_firmware	< 1.0.0.74	cpe:2.3:o:netgear:d7000_firmware::::::::
netgear	d8500_firmware	< 1.0.3.39	cpe:2.3:o:netgear:d8500_firmware::::::::
netgear	dgn2200_firmware	< 1.0.0.102	cpe:2.3:o:netgear:dgn2200_firmware::::::::
netgear	dgn2200b_firmware	< 1.0.0.102	cpe:2.3:o:netgear:dgn2200b_firmware::::::::
netgear	ex3700_firmware	< 1.0.0.70	cpe:2.3:o:netgear:ex3700_firmware::::::::
netgear	ex3800_firmware	< 1.0.0.70	cpe:2.3:o:netgear:ex3800_firmware::::::::
netgear	ex6000_firmware	< 1.0.0.30	cpe:2.3:o:netgear:ex6000_firmware::::::::
netgear	ex6100_firmware	< 1.0.2.22	cpe:2.3:o:netgear:ex6100_firmware::::::::
netgear	ex6120_firmware	< 1.0.0.40	cpe:2.3:o:netgear:ex6120_firmware::::::::
netgear	ex6130_firmware	< 1.0.0.22	cpe:2.3:o:netgear:ex6130_firmware::::::::
netgear	ex6150_firmware	< 1.0.0.38	cpe:2.3:o:netgear:ex6150_firmware::::::::
netgear	ex6200_firmware	< 1.0.3.86	cpe:2.3:o:netgear:ex6200_firmware::::::::
netgear	ex7000_firmware	< 1.0.0.64	cpe:2.3:o:netgear:ex7000_firmware::::::::
netgear	r6250_firmware	< 1.0.4.20	cpe:2.3:o:netgear:r6250_firmware::::::::
netgear	r6300_firmware	< 1.0.4.22	cpe:2.3:o:netgear:r6300_firmware::::::::
netgear	r6400_firmware	< 1.0.1.32	cpe:2.3:o:netgear:r6400_firmware::::::::
netgear	r6400_firmware	< 1.0.2.52	cpe:2.3:o:netgear:r6400_firmware::::::::
netgear	r6700_firmware	< 1.0.1.44	cpe:2.3:o:netgear:r6700_firmware::::::::
netgear	r6900_firmware	< 1.0.1.44	cpe:2.3:o:netgear:r6900_firmware::::::::
netgear	r6900p_firmware	< 1.3.0.18	cpe:2.3:o:netgear:r6900p_firmware::::::::
netgear	r7000_firmware	< 1.0.9.28	cpe:2.3:o:netgear:r7000_firmware::::::::
netgear	r7000p_firmware	< 1.3.0.18	cpe:2.3:o:netgear:r7000p_firmware::::::::
netgear	r7300dst_firmware	< 1.0.0.62	cpe:2.3:o:netgear:r7300dst_firmware::::::::
netgear	r7900_firmware	< 1.0.2.10	cpe:2.3:o:netgear:r7900_firmware::::::::
netgear	r7900p_firmware	< 1.3.0.10	cpe:2.3:o:netgear:r7900p_firmware::::::::
netgear	r8000_firmware	< 1.0.4.12	cpe:2.3:o:netgear:r8000_firmware::::::::
netgear	r8000p_firmware	< 1.3.0.10	cpe:2.3:o:netgear:r8000p_firmware::::::::
netgear	r8300_firmware	< 1.0.2.116	cpe:2.3:o:netgear:r8300_firmware::::::::
netgear	r8500_firmware	< 1.0.2.116	cpe:2.3:o:netgear:r8500_firmware::::::::
netgear	wn2500rp_firmware	< 1.0.1.52	cpe:2.3:o:netgear:wn2500rp_firmware::::::::
netgear	wndr3400_firmware	< 1.0.1.18	cpe:2.3:o:netgear:wndr3400_firmware::::::::
netgear	wnr3500l_firmware	< 1.2.0.46	cpe:2.3:o:netgear:wnr3500l_firmware::::::::

References for CVE-2018-21156

URL	Tags
https://kb.netgear.com/000059474/Security-Advisory-for-Post-Authentication-Buffer-Overflow-on-Some-Gateways-Routers-and-Extenders-PSV-2017-2460	Vendor Advisory

URL

CVE-2018-21156

Exploit prediction scoring system (EPSS) score for CVE-2018-21156

Common vulnerability scoring system (CVSS) metrics for CVE-2018-21156

Weakness enumeration for CVE-2018-21156

Affected software / configurations for CVE-2018-21156

References for CVE-2018-21156