How severe is CVE-2021-3166?

CVE-2021-3166 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-3166 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3166?

CVE-2021-3166 affects Asus Dsl-n14u B1 Firmware. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3166?

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-2021-3166 published?

CVE-2021-3166 was published on 2021-01-18 and last updated on 2026-06-17.

CVE-2021-3166

CVE-2021-3166 is a high-severity vulnerability in Asus Dsl-n14u B1 Firmware with a CVSS 3.x base score of 7.5. 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-434.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 3% (85th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-434
Affected product: Asus Dsl-n14u B1 Firmware
Published: 2021-01-18
Last modified: 2026-06-17

Description

An issue was discovered on ASUS DSL-N14U-B1 1.1.2.3_805 devices. An attacker can upload arbitrary file content as a firmware update when the filename Settings_DSL-N14U-B1.trx is used. Once this file is loaded, shutdown measures on a wide range of services are triggered as if it were a real update, resulting in a persistent outage of those services.

Frequently asked questions

What is CVE-2021-3166?: An issue was discovered on ASUS DSL-N14U-B1 1.1.2.3_805 devices. An attacker can upload arbitrary file content as a firmware update when the filename Settings_DSL-N14U-B1.trx is used. Once this file is loaded, shutdown measures on a wide range of services are triggered as if it were a real update, resulting in a persistent outage of those services.
How severe is CVE-2021-3166?: CVE-2021-3166 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-3166 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3166?: CVE-2021-3166 affects Asus Dsl-n14u B1 Firmware. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3166?: 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-2021-3166 published?: CVE-2021-3166 was published on 2021-01-18 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:o:asus:dsl-n14u_b1_firmware:1.1.2.3_805:*:*:*:*:*:*:*

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