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Weekly Signal
Live intelligence Updated 19 Aug 2026 · 12:58 UTC

Arcadyan, Buffalo · Buffalo Firmware, Wsr-2533dhp3-bk Firmware, Wsr-2533dhpl2-bk Firmware

CVE-2021-20090

Arcadyan Buffalo Firmware Path Traversal Vulnerability

Recommended action

Treat this as an immediate remediation priority. Apply updates per vendor instructions.

View response plan
CVSS9.8
EPSS100.0%
KEVYes
ExploitationConfirmed exploitation
PatchPatch or guidance available ↓

Assessment

Why it matters

CISA lists this vulnerability as known to be exploited; exploitation is confirmed; EPSS is 100.0%; technical severity is CVSS 9.8.

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.

Who should care

  • Teams operating Buffalo Firmware, Wsr-2533dhp3-bk Firmware, Wsr-2533dhpl2-bk Firmware
  • Vulnerability and exposure management teams
  • Security operations teams monitoring exploitation activity

Response plan

What I would do

  1. Confirm whether Buffalo Firmware, Wsr-2533dhp3-bk Firmware, Wsr-2533dhpl2-bk Firmware is present in the environment.
  2. Identify affected versions and establish whether vulnerable services are exposed or reachable.
  3. Apply updates per vendor instructions.
  4. Review relevant security telemetry for evidence of attempted or successful exploitation.
  5. Document the remediation decision and track it to verified completion.

Vendor remediation

Patch and remediation links

Use the vendor source below to confirm the correct fixed version, package or mitigation for your affected product.

Technical details

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE
CWE-22
Affected versions
Arcadyan Buffalo Firmware; Buffalo Wsr-2533dhp3-bk Firmware (End Including: 1.24); Buffalo Wsr-2533dhpl2-bk Firmware (End Including: 1.02)
Published
29 April 2021
Attack vector
Network
Privileges required
None
User interaction
None

Signal timeline

  1. CVE published
  2. Added to CISA KEV
  3. Latest EPSS score: 100.0%
  4. Signal calculated at 85

External references

Live public intelligence This assessment combines public-source evidence. Validate the affected product, version and exposure against your own environment before making a risk decision.