CVE-2021-20090

Arcadyan Buffalo Firmware Path Traversal Vulnerability

Critical 9.8
Exploited: added to CISA KEV 3 Nov 2021

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.

Key facts

Published: 29 Apr 2021
Last changed: 21 Oct 2025
Assigned by: tenable
KEV added: 3 Nov 2021
KEV fix due: 17 Nov 2021
EPSS: 99.982% likely to be exploited in the next 30 days, higher than 99.982% of CVEs (scores for 15 Nov 2026)
SSVC (CISA): Exploitation: active; Automatable: yes; Technical impact: total

Severity scores

Each score is shown as its source gave it. They are not averaged or merged.

9.8CVSS 3.1, Criticalfrom CISA (ADP container)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

What to do

Apply updates per vendor instructions.CISA KEV required action

Historical context and remediation

This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.

No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.

Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.

Read the original CVE record.

Affected products

Vendor	Product	Versions
n/a	Buffalo WSR-2533DHPL2, Buffalo WSR-2533DHP3	WSR-2533DHPL2 <=1.02, WSR-2533DHP3 <= 1.24 (affected)

Timeline

29 Apr 2021 Published
3 Nov 2021 CVE-2021-20090 added to CISA KEV
3 Nov 2021 Added to the CISA KEV catalogue

Weakness

CWE-22

Practice this bug class

HackZoneLabs has a hands-on lab on Path traversal (CWE-22).

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