CVE-2021-20090
Path Traversal in Buffalo Wsr-2533Dhpl2-Bk Firmware ≤ 1.02
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2021-20090 is a critical-severity Path Traversal (CWE-22) vulnerability in Buffalo Wsr-2533Dhpl2-Bk Firmware. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Data Obfuscation (T1001); ranked in the top 0.0% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
A path traversal vulnerability tracked as CVE-2021-20090 affects the web interfaces of Buffalo WSR-2533DHPL2 firmware versions 1.02 and earlier, as well as WSR-2533DHP3 firmware versions 1.24 and earlier. The issue, assigned CWE-22, resides in the devices' HTTP handling logic and permits directory traversal sequences that circumvent built-in authentication checks.
Unauthenticated attackers can reach the flaw remotely over the network with no credentials or user interaction required. Exploitation yields complete control over the router, allowing arbitrary file access, configuration changes, and full compromise of confidentiality, integrity, and availability, consistent with the CVSS 9.8 rating.
Public references, including CERT and SecPod advisories, note that Arcadyan-based routers and modems sharing this firmware lineage are under active exploitation in the wild. The listed sources do not detail specific patches or workarounds, but emphasize the need for immediate firmware updates from Buffalo once available.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-7547
Vulnerability Data
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.
- CWE(s)
- KEV Date Added
- 03 November 2021
Related Threats
Threat-Actor AttributionAI
MITRE ATT&CK Enterprise Techniques
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Affected Assets
Mitigating Controls
Control response
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V5.3.2
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Validates pathnames and filenames to prevent traversal outside intended directories.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Patching/maintenance can remediate known path-traversal flaws in deployed software (partial prevention of exploitability) but does nothing to stop the coding defect from being introduced in the first place.
PR.AA-05 defines and reviews access policies but does not address code-level pathname neutralization, so neither direction prevents CWE-22.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.