Threats / Arcadyan / CVE-2021-20090
CVE-2021-20090
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Arcadyan Buffalo Firmware vulnerability
Arcadyan Buffalo firmware contains a path traversal vulnerability allowing unauthenticated remote attackers to bypass authentication and access sensitive information.
Verdict
Today item — known-exploited.
A path traversal flaw in Buffalo firmware enables unauthenticated remote exploitation to circumvent access controls and retrieve sensitive data. Active exploitation in the wild and high EPSS score indicate immediate risk to affected router deployments.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
34 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03).
Probability (EPSS)
EPSS 0.99983 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Arcadyan, Buffalo Firmware. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-22 Path Traversal — weakness family: Path traversal / file.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious request with path traversal sequences to bypass the authentication mechanism on the target router.
Business
Attackers gain unauthorized access to router administration interfaces without credentials, enabling further network compromise.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I navigate the filesystem using directory traversal payloads to locate and exfiltrate configuration files and sensitive data stored on the device.
Business
Confidential network settings, credentials, and user data are exposed, creating risk of lateral movement and credential theft.
3
Lateral reach — past segmentation narrative 3
Attacker
I leverage the unauthenticated access to modify router configurations or inject malicious content for persistent compromise.
Business
The compromised router becomes a persistent foothold for network infiltration, man-in-the-middle attacks, and malware distribution.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05