Authentication bypass via encoded parent-directory paths
Published Apr 29, 2021 · Updated Oct 21, 2025
Path traversal in Buffalo WSR-2533DHPL2 1.02 and earlier and WSR-2533DHP3 1.24 and earlier allows remote attackers to bypass authentication. The Arcadyan web interface treats images, js, and css directories as authentication bypass paths, then resolves encoded parent-directory segments to protected pages. No credentials or user interaction are required; exposed management access permits reading protected pages and tokens that can authorize router-setting changes.
Summary
What happened
Path traversal in Buffalo WSR-2533DHPL2 1.02 and earlier and WSR-2533DHP3 1.24 and earlier allows remote attackers to bypass authentication. The Arcadyan web interface treats images, js, and css directories as authentication bypass paths, then resolves encoded parent-directory segments to protected pages. No credentials or user interaction are required; exposed management access permits reading protected pages and tokens that can authorize router-setting changes.
The record
- CVE
- CVE-2021-20090
- Published
- Apr 29, 2021
- Updated
- Oct 21, 2025
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-22, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 29, 2021CVE publishedPublication date reported by the CVE source.
- Oct 21, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
What conditions does exploitation require?
What is affected?
Affected products and versions are unavailable in this record.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- Encoded bypass-directory path traversal proof of conceptfunctional · demonstrated
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Reported exploitation
- CISA Known Exploited Vulnerabilities catalog listingknown exploited catalog
- Mirai botnet variant deployment through affected routersbotnet
Technologies
Your stack
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Your stack
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