Hazard

Is CVE-2021-20090 being exploited?

Weaponised and widely attempted

Reliable public exploit code exists, or mass exploitation attempts are probable. Patch inside days, not weeks.

Arcadyan Buffalo Firmware Path Traversal Vulnerability

Arcadyan · Buffalo Firmware

CVSS 9.8 EPSS 100% no public exploit indexed Fix deadline passed 17 November 2021

What it is

Arcadyan Buffalo firmware contains a path traversal vulnerability that could allow unauthenticated, remote attackers to bypass authentication and access sensitive information. This vulnerability affects multiple routers across several different vendors.

Why we say that

  • EPSS puts exploitation in the next 30 days at 100%
  • CISA's federal remediation deadline (2021-11-17) has passed
  • CVSS 9.8 critical
  • Listed in the CISA Known Exploited Vulnerabilities catalogue

Every line above comes from a named public source. Where the evidence is thin, we say so rather than inventing confidence — see methodology.

What to do

Apply updates per vendor instructions.

What it costs when this goes wrong

This is where UK enforcement meets the vulnerability record. Where an unfixed vulnerability leads to a breach, the ICO treats it as a security failure under UK GDPR. Recent cases:

All UK cases caused by unpatched software →