VulnTideExploited vulnerabilities, by vendor. Data as of 28 Oct 2026.
Known exploitedIn CISA's KEV catalog since 3 November 2021Ransomware use: unknown
Arcadyan Buffalo Firmware

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

Is it exploited?

Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 3 Nov 2021, 188 days after the CVE record was published.

How likely is exploitation in the next 30 days?
100%

EPSS score, percentile 100 of all scored records

How severe?
9.8 Critical

CVSS v3.1 base score, from CISA's enrichment of the record

What should I do?

CISA deadline 17 Nov 2021. Apply updates per vendor instructions.

The CVE record links no vendor advisory, patch or mitigation.

Which versions are affected?

Affected

  • WSR-2533DHPL2 <=1.02, WSR-2533DHP3 <= 1.24

Versions by product

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

What to do

Required action, set by CISA

Apply updates per vendor instructions.

CISA due date for this action: 17 November 2021.

Advisories and patches

The CVE record links no vendor advisory, patch or mitigation.

Linked from CISA's catalog entry

Affected products and versions

As listed in the CVE record.

n/a Buffalo WSR-2533DHPL2, Buffalo WSR-2533DHP3
StatusVersions
AffectedWSR-2533DHPL2 <=1.02, WSR-2533DHP3 <= 1.24

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

About this 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.

Summary: CISA's KEV catalog, as of 28 Oct 2026.

  • CISA added CVE-2021-20090 to its Known Exploited Vulnerabilities (KEV) catalog on 3 Nov 2021.
  • CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
  • The due date CISA sets for the required action is 17 Nov 2021.
  • The CVE record was published on 29 Apr 2021, 188 days before it was added to KEV.
  • The CVE record carries a CVSS v3.1 base score of 9.8 (Critical), taken from CISA's enrichment of the record.
  • FIRST's EPSS model puts the probability of exploitation in the next 30 days at 100% (percentile 100), as of 28 Oct 2026.
  • CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact total.

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.

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.

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

Weakness

  • CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.

Timeline

DateEvent
29 Apr 2021CVE record published
3 Nov 2021Added to CISA KEV
17 Nov 2021CISA due date for the required action
21 Oct 2025CVE record last updated

References