How severe is CVE-2021-20090?

CVE-2021-20090 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-20090 being actively exploited?

Yes. CVE-2021-20090 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2021-11-03, which means active exploitation has been confirmed. It should be prioritised for remediation.

What products are affected by CVE-2021-20090?

CVE-2021-20090 primarily affects Buffalo Wsr-2533dhpl2-bk Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-20090?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.

Does CVE-2021-20090 have an EU (EUVD) identifier?

Yes. CVE-2021-20090 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-7547. It is also flagged as exploited in the EUVD (since 2021-11-03).

When was CVE-2021-20090 published?

CVE-2021-20090 was published on 2021-04-29 and last updated on 2026-06-17.

CVE-2021-20090

CVE-2021-20090 is a critical-severity vulnerability in Buffalo Wsr-2533dhpl2-bk Firmware with a CVSS 3.x base score of 9.8. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2021-11-03). The underlying weakness is classified as CWE-22.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 100% (100th percentile)
Actively exploited: Yes — listed in CISA KEV (added 2021-11-03)
EU (EUVD) id: EUVD-2021-7547
EU exploitation: Flagged exploited in the ENISA EU Vulnerability Database (since 2021-11-03)
Weakness: CWE-22
Affected product: Buffalo Wsr-2533dhpl2-bk Firmware
Published: 2021-04-29
Last modified: 2026-06-17

Description

A path traversal vulnerability in the web interfaces of Buffalo WSR-2533DHPL2 firmware version <= 1.02 and WSR-2533DHP3 firmware version <= 1.24 could allow unauthenticated remote attackers to bypass authentication.

Frequently asked questions

What is CVE-2021-20090?: A path traversal vulnerability in the web interfaces of Buffalo WSR-2533DHPL2 firmware version <= 1.02 and WSR-2533DHP3 firmware version <= 1.24 could allow unauthenticated remote attackers to bypass authentication.
How severe is CVE-2021-20090?: CVE-2021-20090 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-20090 being actively exploited?: Yes. CVE-2021-20090 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2021-11-03, which means active exploitation has been confirmed. It should be prioritised for remediation.
What products are affected by CVE-2021-20090?: CVE-2021-20090 primarily affects Buffalo Wsr-2533dhpl2-bk Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-20090?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.
Does CVE-2021-20090 have an EU (EUVD) identifier?: Yes. CVE-2021-20090 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-7547. It is also flagged as exploited in the EUVD (since 2021-11-03).
When was CVE-2021-20090 published?: CVE-2021-20090 was published on 2021-04-29 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:o:buffalo:wsr-2533dhpl2-bk_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:buffalo:wsr-2533dhp3-bk_firmware:*:*:*:*:*:*:*:*

More vulnerabilities in Buffalo Wsr-2533dhpl2-bk Firmware

CVE-2021-20091 — High (CVSS 8.8): The web interfaces of Buffalo WSR-2533DHPL2 firmware version <= 1.02 and WSR-2533DHP3 firmware version <= 1.24 do not…
CVE-2021-20092 — High (CVSS 7.5): The web interfaces of Buffalo WSR-2533DHPL2 firmware version <= 1.02 and WSR-2533DHP3 firmware version <= 1.24 do not…

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