CVE-2021-20090
CRITICALCISA KEVEPSS 100th pctlDescription
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 to fix
Actively exploited, no published fix found yet
CISA required action: Apply updates per vendor instructions.
Federal remediation due: 2021-11-17
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploit Intelligence
Very high risk: more likely to be exploited than 100% of all known CVEs.
Arcadyan Buffalo Firmware Path Traversal Vulnerability
Arcadyan Buffalo firmware contains a path traversal vulnerability that could allow unauthenticated, remote attackers to bypass authentication and access sensitive information. This vulnerability affects multiple routers across several different vendors.
Apply updates per vendor instructions.
Remediation due: 2021-11-17
References
Related Vulnerabilities
Other CWE-22 (Path Traversal) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2024-23897 | Critical | 9.8 | 100% | KEV + Ransom | Fix |
| CVE-2023-32315 | High | 8.6 | 100% | KEV | Fix |
| CVE-2022-29464 | Critical | 9.8 | 100% | KEV + Ransom | - |
| CVE-2021-26086 | Medium | 5.3 | 100% | KEV | Fix |
| CVE-2021-22005 | Critical | 9.8 | 100% | KEV + Ransom | Fix |
| CVE-2020-5902 | Critical | 9.8 | 100% | KEV + Ransom | Fix |
Common questions
How do I fix CVE-2021-20090?
No published fix for CVE-2021-20090 has been found yet. It is on the CISA Known Exploited Vulnerabilities list; federal agencies must remediate by 2021-11-17. Apply the vendor's mitigations per CISA's guidance.
Is CVE-2021-20090 being actively exploited?
Yes. CVE-2021-20090 is listed in the CISA Known Exploited Vulnerabilities catalog, which means exploitation has been observed in the wild. US federal agencies were required to remediate it by 2021-11-17. Treat it as a priority whatever its CVSS score says.
How severe is CVE-2021-20090?
CVE-2021-20090 has a CVSS v3 base score of 9.8, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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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 2025-11-03.