CVE intelligence and bounded remediation

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

Critical CVSS 9.8 CISA KEV

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.

Severity
Critical
CVSS
9.8 (3.1)
Published
2021-04-29
CISA KEV
Known exploited
Ecosystem
operating-system
Weaknesses
CWE-22

Affected products

  • buffalo / wsr-2533dhpl2-bk_firmware
  • buffalo / wsr-2533dhp3-bk_firmware

Matched remediation archetype

Path traversal, unsafe upload, and file handling

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Check exposure

  • Trace untrusted filenames, archive entries, URLs, and path segments into read, write, include, extraction, and upload operations.
  • Identify filesystem roots, mount permissions, symbolic-link behavior, archive handling, and whether uploaded content is web-accessible or executable.
  • Review canonicalization and containment checks across supported operating systems and storage backends.

Remediate safely

  • Generate server-side storage identifiers and resolve paths beneath a fixed root using filesystem-aware containment checks.
  • Reject absolute, parent-relative, alternate-separator, device, link, and archive entries that escape the intended root.
  • Store uploads outside executable or served paths, validate type and size, and use private atomic temporary files.

Authoritative sources

Complete CVE record and remediation plan

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