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PatchSiren cyber security CVE debrief

CVE-2021-20090 Arcadyan CVE debrief

CVE-2021-20090 is a path traversal vulnerability in Arcadyan Buffalo Firmware that CISA has placed in its Known Exploited Vulnerabilities catalog. Because it is on the KEV list, defenders should treat it as an urgent remediation item and follow the vendor’s update guidance without delay.

Vendor
Arcadyan
Product
Buffalo Firmware
CVSS
Unknown
CISA KEV
Listed
Original CVE published
2021-11-03
Original CVE updated
2021-11-03
Advisory published
2021-11-03
Advisory updated
2021-11-03

Who should care

Organizations that operate Arcadyan Buffalo Firmware, along with security and patch management teams responsible for tracking CISA KEV items and vendor firmware updates.

Technical summary

The supplied official records identify CVE-2021-20090 as a path traversal vulnerability affecting Arcadyan Buffalo Firmware. CISA classifies it as a known exploited vulnerability and directs users to apply updates per vendor instructions. The provided corpus does not include affected version ranges, a CVSS score, or additional verified technical detail.

Defensive priority

Urgent. CISA added this issue to the KEV catalog on 2021-11-03 with a remediation due date of 2021-11-17, so it should be prioritized ahead of non-KEV issues.

Recommended defensive actions

  • Confirm whether Arcadyan Buffalo Firmware is deployed in your environment.
  • Identify all affected devices, models, and firmware instances that require remediation.
  • Apply the vendor-provided update or mitigation guidance as soon as possible.
  • Validate that remediation completed successfully across all exposed assets.
  • Track CISA KEV updates and the vendor/NVD advisories for any follow-on guidance.

Evidence notes

CISA’s KEV entry names the issue “Arcadyan Buffalo Firmware Path Traversal Vulnerability,” marks it as exploited, and instructs users to apply updates per vendor instructions. The supplied record also links to the official CVE and NVD pages. No CVSS score was provided in the supplied corpus.

Official resources

CVE-2021-20090 was published and modified on 2021-11-03. CISA added it to the KEV catalog on 2021-11-03 with a due date of 2021-11-17. This debrief uses only the supplied official records and KEV metadata.