CVE-2021-27255 [High] | Security Vulnerability in Br200 Firmware

This vulnerability allows remote attackers to execute arbitrary code on affected installations of NETGEAR R7800 firmware version 1.0.2.76. Authentication is not required to exploit this vulnerability. The specific flaw exists within the refresh_status.aspx endpoint. The issue results from a lack of authentication required to start a service on the server. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-12360.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	1.67%	1.26%	-0.40%
2	2025-07-27	1.23%	1.67%	+0.43%
3	2025-03-30	—	1.23%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

1.67%

1.26%

-0.40%

2025-07-27

1.23%

1.67%

+0.43%

2025-03-30

—

1.23%

—

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]
6.3	3.0	MEDIUM	`CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L` 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:L) Some sensitive info could get out, but not a total data dump. Integrity (I:L) Attackers could change some data, but it’s limited—not everything goes. Availability (A:L) Might cause slowdowns, glitches, or partial disruption—not a full brick.	2.8	3.4	[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]

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]

6.3

3.0

MEDIUM

CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L 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:L): Some sensitive info could get out, but not a total data dump.
Integrity (I:L): Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L): Might cause slowdowns, glitches, or partial disruption—not a full brick.

2.8

3.4

[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]

Affected software / configurations for CVE-2021-27255

Vendor	Product	Version	Raw CPE
netgear	br200_firmware	< 5.10.0.5	cpe:2.3:o:netgear:br200_firmware::::::::
netgear	br500_firmware	< 5.10.0.5	cpe:2.3:o:netgear:br500_firmware::::::::
netgear	d7800_firmware	< 1.0.1.60	cpe:2.3:o:netgear:d7800_firmware::::::::
netgear	ex6100v2_firmware	< 1.0.1.98	cpe:2.3:o:netgear:ex6100v2_firmware::::::::
netgear	ex6150v2_firmware	< 1.0.1.98	cpe:2.3:o:netgear:ex6150v2_firmware::::::::
netgear	ex6250_firmware	< 1.0.0.134	cpe:2.3:o:netgear:ex6250_firmware::::::::
netgear	ex6400_firmware	< 1.0.2.158	cpe:2.3:o:netgear:ex6400_firmware::::::::
netgear	ex6400v2_firmware	< 1.0.0.134	cpe:2.3:o:netgear:ex6400v2_firmware::::::::
netgear	ex6410_firmware	< 1.0.0.134	cpe:2.3:o:netgear:ex6410_firmware::::::::
netgear	ex6420_firmware	< 1.0.0.134	cpe:2.3:o:netgear:ex6420_firmware::::::::
netgear	ex7300_firmware	< 1.0.2.158	cpe:2.3:o:netgear:ex7300_firmware::::::::
netgear	ex7300v2_firmware	< 1.0.0.134	cpe:2.3:o:netgear:ex7300v2_firmware::::::::
netgear	ex7320_firmware	< 1.0.0.134	cpe:2.3:o:netgear:ex7320_firmware::::::::
netgear	ex7700_firmware	< 1.0.0.216	cpe:2.3:o:netgear:ex7700_firmware::::::::
netgear	ex8000_firmware	< 1.0.1.232	cpe:2.3:o:netgear:ex8000_firmware::::::::
netgear	lbr20_firmware	< 2.6.3.50	cpe:2.3:o:netgear:lbr20_firmware::::::::
netgear	r7800_firmware	< 1.0.2.80	cpe:2.3:o:netgear:r7800_firmware::::::::
netgear	r8900_firmware	< 1.0.5.28	cpe:2.3:o:netgear:r8900_firmware::::::::
netgear	r9000_firmware	< 1.0.5.28	cpe:2.3:o:netgear:r9000_firmware::::::::
netgear	rbk12_firmware	< 2.7.2.104	cpe:2.3:o:netgear:rbk12_firmware::::::::
netgear	rbk13_firmware	< 2.7.2.104	cpe:2.3:o:netgear:rbk13_firmware::::::::
netgear	rbk14_firmware	< 2.7.2.104	cpe:2.3:o:netgear:rbk14_firmware::::::::
netgear	rbk15_firmware	< 2.7.2.104	cpe:2.3:o:netgear:rbk15_firmware::::::::
netgear	rbk20_firmware	< 2.6.2.104	cpe:2.3:o:netgear:rbk20_firmware::::::::
netgear	rbk23_firmware	< 2.7.2.104	cpe:2.3:o:netgear:rbk23_firmware::::::::
netgear	rbk40_firmware	< 2.6.2.104	cpe:2.3:o:netgear:rbk40_firmware::::::::
netgear	rbk43_firmware	< 2.6.2.104	cpe:2.3:o:netgear:rbk43_firmware::::::::
netgear	rbk43s_firmware	< 2.6.2.104	cpe:2.3:o:netgear:rbk43s_firmware::::::::
netgear	rbk44_firmware	< 2.6.2.104	cpe:2.3:o:netgear:rbk44_firmware::::::::
netgear	rbk50_firmware	< 2.7.2.104	cpe:2.3:o:netgear:rbk50_firmware::::::::
netgear	rbk53_firmware	< 2.7.2.104	cpe:2.3:o:netgear:rbk53_firmware::::::::
netgear	rbr10_firmware	< 2.6.2.104	cpe:2.3:o:netgear:rbr10_firmware::::::::
netgear	rbr20_firmware	< 2.6.2.104	cpe:2.3:o:netgear:rbr20_firmware::::::::
netgear	rbr40_firmware	< 2.6.2.104	cpe:2.3:o:netgear:rbr40_firmware::::::::
netgear	rbr50_firmware	< 2.7.2.104	cpe:2.3:o:netgear:rbr50_firmware::::::::
netgear	rbs10_firmware	< 2.6.2.104	cpe:2.3:o:netgear:rbs10_firmware::::::::
netgear	rbs20_firmware	< 2.6.2.104	cpe:2.3:o:netgear:rbs20_firmware::::::::
netgear	rbs40_firmware	< 2.6.2.104	cpe:2.3:o:netgear:rbs40_firmware::::::::
netgear	rbs50_firmware	< 2.7.2.104	cpe:2.3:o:netgear:rbs50_firmware::::::::
netgear	rbs50y_firmware	< 2.6.2.104	cpe:2.3:o:netgear:rbs50y_firmware::::::::
netgear	xr450_firmware	< 2.3.2.114	cpe:2.3:o:netgear:xr450_firmware::::::::
netgear	xr500_firmware	< 2.3.2.114	cpe:2.3:o:netgear:xr500_firmware::::::::
netgear	xr700_firmware	< 1.0.1.38	cpe:2.3:o:netgear:xr700_firmware::::::::

References for CVE-2021-27255

URL	Tags
https://kb.netgear.com/000062883/Security-Advisory-for-Multiple-Vulnerabilities-on-Some-Routers-Satellites-and-Extenders	Patch Vendor Advisory
https://www.zerodayinitiative.com/advisories/ZDI-21-263/	Third Party Advisory VDB Entry

URL

CVE-2021-27255

Exploit prediction scoring system (EPSS) score for CVE-2021-27255

Common vulnerability scoring system (CVSS) metrics for CVE-2021-27255

Weakness enumeration for CVE-2021-27255

Affected software / configurations for CVE-2021-27255

References for CVE-2021-27255