CVE-2021-20090: Arcadyan Buffalo Firmware Path Traversal Vulnerability

CISA Known Exploited Vulnerabilities

Name

Arcadyan Buffalo Firmware Path Traversal Vulnerability

Vendor

Arcadyan

Product

Buffalo Firmware

Added to the catalog

2021-11-03

Due date for US federal agencies

2021-11-17

Weaknesses

CWE-22

Catalog version

2026.10.30

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.

Required action (CISA)

Apply updates per vendor instructions.

Ransomware use: CISA does not mark known use of this vulnerability in ransomware campaigns.

Links in CISA's notes

• https://nvd.nist.gov/vuln/detail/CVE-2021-20090

Read on 2026-11-02T23:39:54.475Z under licence cisa-kev-cc0@b0067899 from https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

NVD analysis

Status

Analyzed

Published

2021-04-29T15:15:10.630

Last modified

2026-06-17T03:33:15.487

Weaknesses

CWE-22

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.

References

• https://www.kb.cert.org/vuls/id/914124 (Third Party Advisory, US Government Resource)
• https://www.secpod.com/blog/arcadyan-based-routers-and-modems-under-active-exploitation/ (Exploit, Third Party Advisory)
• https://www.tenable.com/security/research/tra-2021-13 (Exploit, Third Party Advisory)
• https://www.kb.cert.org/vuls/id/914124 (Third Party Advisory, US Government Resource)
• https://www.secpod.com/blog/arcadyan-based-routers-and-modems-under-active-exploitation/ (Exploit, Third Party Advisory)
• https://www.tenable.com/security/research/tra-2021-13 (Exploit, Third Party Advisory)
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-20090 (US Government Resource)

This product uses the NVD API but is not endorsed or certified by the NVD.

Read on 2026-11-02T23:41:51.476Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2021-20090

CVE record

Assigner

tenable

State

PUBLISHED

Published

2021-04-29T00:00:00.000Z

Updated

2025-10-21T23:25:47.628Z

Problem types

Path Traversal

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.

References

• https://www.tenable.com/security/research/tra-2021-13
• VU#914124
• https://www.secpod.com/blog/arcadyan-based-routers-and-modems-under-active-exploitation/

Read on 2026-11-03T01:05:49.237Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2021/20xxx/CVE-2021-20090.json

Detection rules (SigmaHQ)

SigmaHQ rules whose own tags name this CVE. Each rule page shows the rule as its author published it.

• Arcadyan Router Exploitations (status test, level critical)

Defensive techniques (MITRE D3FEND)

D3FEND maps these defensive techniques to the weakness (CWE) that NVD lists for this CVE, through the digital artifacts the weakness affects. D3FEND does not say they stop this vulnerability.

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