How severe is CVE-2018-21203?

CVE-2018-21203 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2018-21203 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (51st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-21203?

CVE-2018-21203 primarily affects Netgear R6100 Firmware. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2018-21203?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2018-21203 published?

CVE-2018-21203 was published on 2020-04-28 and last updated on 2026-06-17.

CVE-2018-21203

CVE-2018-21203 is a high-severity vulnerability in Netgear R6100 Firmware with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v2: 5.8
EPSS exploit prediction: 1% (51st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Netgear R6100 Firmware
Published: 2020-04-28
Last modified: 2026-06-17

Description

Certain NETGEAR devices are affected by a stack-based buffer overflow by an unauthenticated attacker. This affects R6100 before 1.0.1.20, R9000 before 1.0.2.52, WNDR3700v4 before 1.0.2.96, WNDR4300 before 1.0.2.98, WNDR4300v2 before 1.0.0.50, and WNDR4500v3 before 1.0.0.50.

Frequently asked questions

What is CVE-2018-21203?: Certain NETGEAR devices are affected by a stack-based buffer overflow by an unauthenticated attacker. This affects R6100 before 1.0.1.20, R9000 before 1.0.2.52, WNDR3700v4 before 1.0.2.96, WNDR4300 before 1.0.2.98, WNDR4300v2 before 1.0.0.50, and WNDR4500v3 before 1.0.0.50.
How severe is CVE-2018-21203?: CVE-2018-21203 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2018-21203 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (51st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-21203?: CVE-2018-21203 primarily affects Netgear R6100 Firmware. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2018-21203?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2018-21203 published?: CVE-2018-21203 was published on 2020-04-28 and last updated on 2026-06-17.

References

https://kb.netgear.com/000055146/Security-Advisory-for-Pre-Authentication-Stack-Overflow-on-Some-Routers-PSV-2017-2589

Affected products (5)

cpe:2.3:o:netgear:r6100_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:r9000_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:wndr3700_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:wndr4300_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:netgear:wndr4500_firmware:*:*:*:*:*:*:*:*

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