Is CVE-2021-27239 in the CISA KEV catalog?

No. CVE-2021-27239 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-27239?

CVE-2021-27239 has a CVSS v3 base score of 8.8 (HIGH).

What is the EPSS score for CVE-2021-27239?

CVE-2021-27239 has an EPSS score of 0.75% (50th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-27239?

Upgrade d6220 firmware to 1.0.0.68 or later. Fixes are available for 34 affected products.

CVE & CISA-KEV Catalog

CVE-2021-27239

HIGH

8.8

CVSS v3

NVD

Description

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.

CWE-121Stack-based Buffer Overflow

How to fix

Remediation Available

d6220 firmwareNVD

Affected:< 1.0.0.68Fixed in:1.0.0.68CVE-2021-27239derived from NVD

d6400 firmwareNVD

Affected:< 1.0.0.102Fixed in:1.0.0.102CVE-2021-27239derived from NVD

d7000 firmwareNVD

Affected:< 1.0.0.66Fixed in:1.0.0.66CVE-2021-27239derived from NVD

d8500 firmwareNVD

Affected:< 1.0.3.60Fixed in:1.0.3.60CVE-2021-27239derived from NVD

dc112a firmwareNVD

Affected:< 1.0.0.54Fixed in:1.0.0.54CVE-2021-27239derived from NVD

ex7000 firmwareNVD

Affected:< 1.0.1.94Fixed in:1.0.1.94CVE-2021-27239derived from NVD

ex7500 firmwareNVD

Affected:< 1.0.0.72Fixed in:1.0.0.72CVE-2021-27239derived from NVD

r6250 firmwareNVD

Affected:< 1.0.4.48Fixed in:1.0.4.48CVE-2021-27239derived from NVD

r6300 firmwareNVD

Affected:< 1.0.4.50Fixed in:1.0.4.50CVE-2021-27239derived from NVD

r6400 firmwareNVD

Affected:< 1.0.4.102Fixed in:1.0.4.102CVE-2021-27239derived from NVD

r6700 firmwareNVD

Affected:< 1.0.4.102Fixed in:1.0.4.102CVE-2021-27239derived from NVD

r6900p firmwareNVD

Affected:< 1.3.2.132Fixed in:1.3.2.132CVE-2021-27239derived from NVD

r7000 firmwareNVD

Affected:< 1.0.11.116Fixed in:1.0.11.116CVE-2021-27239derived from NVD

r7000p firmwareNVD

Affected:< 1.3.2.132Fixed in:1.3.2.132CVE-2021-27239derived from NVD

r7100lg firmwareNVD

Affected:< 1.0.0.64Fixed in:1.0.0.64CVE-2021-27239derived from NVD

r7850 firmwareNVD

Affected:< 1.0.5.68Fixed in:1.0.5.68CVE-2021-27239derived from NVD

r7900 firmwareNVD

Affected:< 1.0.4.38Fixed in:1.0.4.38CVE-2021-27239derived from NVD

r7900p firmwareNVD

Affected:< 1.4.1.68Fixed in:1.4.1.68CVE-2021-27239derived from NVD

r7960p firmwareNVD

Affected:< 1.4.1.68Fixed in:1.4.1.68CVE-2021-27239derived from NVD

r8000 firmwareNVD

Affected:< 1.0.4.68Fixed in:1.0.4.68CVE-2021-27239derived from NVD

r8000p firmwareNVD

Affected:< 1.4.1.68Fixed in:1.4.1.68CVE-2021-27239derived from NVD

r8300 firmwareNVD

Affected:< 1.0.2.144Fixed in:1.0.2.144CVE-2021-27239derived from NVD

r8500 firmwareNVD

Affected:< 1.0.2.144Fixed in:1.0.2.144CVE-2021-27239derived from NVD

rax200 firmwareNVD

Affected:< 1.0.2.88Fixed in:1.0.2.88CVE-2021-27239derived from NVD

rax75 firmwareNVD

Affected:< 1.0.3.102Fixed in:1.0.3.102CVE-2021-27239derived from NVD

rax80 firmwareNVD

Affected:< 1.0.3.102Fixed in:1.0.3.102CVE-2021-27239derived from NVD

rbr750 firmwareNVD

Affected:< 3.2.17.12Fixed in:3.2.17.12CVE-2021-27239derived from NVD

rbr850 firmwareNVD

Affected:< 3.2.17.12Fixed in:3.2.17.12CVE-2021-27239derived from NVD

rbs40v firmwareNVD

Affected:< 2.6.2.4Fixed in:2.6.2.4CVE-2021-27239derived from NVD

rbs750 firmwareNVD

Affected:< 3.2.17.12Fixed in:3.2.17.12CVE-2021-27239derived from NVD

rbs850 firmwareNVD

Affected:< 3.2.17.12Fixed in:3.2.17.12CVE-2021-27239derived from NVD

wndr3400 firmwareNVD

Affected:< 1.0.1.38Fixed in:1.0.1.38CVE-2021-27239derived from NVD

wnr3500l firmwareNVD

Affected:< 1.2.0.66Fixed in:1.2.0.66CVE-2021-27239derived from NVD

xr300 firmwareNVD

Affected:< 1.0.3.56Fixed in:1.0.3.56CVE-2021-27239derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorAdjacent

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

0.75%probability of exploitation in 30 days

50thpercentile

Moderate risk: more likely to be exploited than 50% of all known CVEs.

References

Vendor Advisory1

kb.netgear.com

Third-Party Advisory1

zerodayinitiative.com

Related Vulnerabilities

Other CWE-121 (Stack-based Buffer Overflow) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-22457	Critical	9.0	100%	KEV + Ransom	Fix
CVE-2025-0282	Critical	9.0	100%	KEV + Ransom	-
CVE-2021-20038	Critical	9.8	100%	KEV + Ransom	-
CVE-2009-0927	High	8.8	97%	KEV	Fix
CVE-2020-10924	High	8.8	87%	-	-
CVE-2022-20705	Critical	10.0	80%	-	-

Embed a live status badge for CVE-2021-27239

Markdown

[![CVE-2021-27239](https://tridentstack.com/cve/badge/CVE-2021-27239.svg)](https://tridentstack.com/cve/CVE-2021-27239)

HTML

<a href="https://tridentstack.com/cve/CVE-2021-27239"><img src="https://tridentstack.com/cve/badge/CVE-2021-27239.svg" alt="CVE-2021-27239"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

Start free

This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.