What is the CVSS score of CVE-2021-27251?

CVE-2021-27251 has a CVSS 3.1 base score of 8.8 (High). CVSS vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.7%.

Is there a patch available for CVE-2021-27251?

Yes, a patch is available for CVE-2021-27251. Update the affected software to the latest version immediately.

Ex6150 Firmware CVE-2021-27251

HIGH

Cleartext Transmission of Sensitive Information (CWE-319)

2021-04-14 zdi-disclosures@trendmicro.com

RCE Netgear Ex6150 Firmware R8900 Firmware R9000 Firmware Rbr20 Firmware Rbs20 Firmware Ex8000 Firmware D7800 Firmware R7800 Firmware Xr500 Firmware Xr700 Firmware Rbk20 Firmware Rbr40 Firmware Rbs40 Firmware Rbk40 Firmware Rbr50 Firmware Rbs50 Firmware Rbk50 Firmware Ex6400 Firmware Ex7300 Firmware Xr450 Firmware Rbs50Y Firmware Ex7700 Firmware Rbk12 Firmware Rbr10 Firmware Rbs10 Firmware Ex6100V2 Firmware Ex6250 Firmware Ex6400V2 Firmware Ex6410 Firmware Ex7300V2 Firmware Ex7320 Firmware Rbk13 Firmware Rbk14 Firmware Rbk15 Firmware Br200 Firmware Br500 Firmware Ex6420 Firmware Lbr20 Firmware Rbk23 Firmware Rbk43 Firmware Rbk43S Firmware Rbk44 Firmware Rbk53 Firmware

8.8

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-319 OWASP Top 10:2025 A04:2025 - Cryptographic Failures ASVS 5.0 V12 - Secure Communication Transport encryption
Impact	CVSS score of 8.8 (HIGH). Attack characteristics: adjacent network attack vector, low complexity, no privileges required, no user interaction not required.
Exploit ScenarioDerived	Successful exploitation could compromise the high-severity affected system.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

Patch available 0.7% exploitation probability (EPSS)

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AnalysisAI

This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR Nighthawk R7800. Rated high severity (CVSS 8.8), this vulnerability is no authentication required, low attack complexity.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affects your stack

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Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified under CWE-319. This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR Nighthawk R7800. Authentication is not required to exploit this vulnerability The specific flaw exists within handling of firmware updates. The issue results from a fallback to a insecure protocol to deliver updates. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-12308. Affected products include: Netgear Br200 Firmware, Netgear Br500 Firmware, Netgear D7800 Firmware, Netgear Ex6100V2 Firmware, Netgear Ex6150 Firmware.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 8.8 HIGH

AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Adjacent

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

DescriptionNVD

This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR Nighthawk R7800. Authentication is not required to exploit this vulnerability The specific flaw exists within handling of firmware updates. The issue results from a fallback to a insecure protocol to deliver updates. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-12308.

Threat Intelligence Overview

EPSS Score

0.7%

Top 50% exploitable

Data Quality

2 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC No

EPSS 0.7%

Patch available Yes

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

None

System Exposure· derived

Controlled

Automatable· derived

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +1

CVSS: +44

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Remote Code Execution CRITICAL

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

Affected Products (CPE)NVD

cpe:2.3:o:netgear:br200_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:br500_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:d7800_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:ex6100v2_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:ex6150_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:ex6250_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:ex6400_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:ex6400v2_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:ex6410_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:ex6420_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:ex7300_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:ex7300v2_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:ex7320_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:ex7700_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:ex8000_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:lbr20_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:r7800_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:r8900_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:r9000_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:netgear:rbk12_firmware:*:*:*:*:*:*:*:*

+ 23 more

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References

Advisories & patches

PATCH https://kb.netgear.com/000062883/Security-Advisory-for-Multiple-Vulnerabilities-on-Some-Routers-Satellites-and-Extenders REF https://www.zerodayinitiative.com/advisories/ZDI-21-247/

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