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CVE-2021-20090

CRITICAL
9.8
CVSS Score
Published: April 29, 2021 at 12:00 AM UTC
Updated: June 17, 2026 at 03:33 AM UTC
6 products affected across 1 vendorWsr 2533DHPL2 Bk FirmwareWsr 2533DHP3 Bk FirmwareWsr-2533Dhpl2-Bk

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Severity
CRITICAL9.8
Exploitation
CISA KEV
Exploit prediction
EPSS 100%
SSVC
Active

Actively Exploited

CISA Known Exploited Vulnerabilities (KEV) Catalog

EPSS Score100.0%

EPSS (Exploit Prediction Scoring System) estimates a 100.0% chance this CVE is exploited in the wild within the next 30 days — higher than 100% of all CVEs. It complements CVSS: a high EPSS on a mid-severity CVE can still be urgent.

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.

Required Action
Apply updates per vendor instructions.
Ransomware Use
Unknown
Added to KEV
Nov 3, 2021
Remediation Due
Nov 17, 2021
1809 days overdue
Notes
https://nvd.nist.gov/vuln/detail/CVE-2021-20090

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Wsr 2533DHP3 Bk Firmware· Buffalo
95%
v ≤ 1.24
buffalo-wsr-2533dhp3-bk (same device)
Wsr 2533DHPL2 Bk Firmware· Buffalo
95%
v ≤ 1.02
buffalo-wsr-2533dhpl2-bk (same device)
WSR-2533DHP3· Buffalo
60%
v ≤ 1.02
WSR-2533DHPL2· Buffalo
60%
v ≤ 1.02
Wsr-2533Dhp3-Bk· Buffalodevice
80%
All versions
Wsr-2533Dhpl2-Bk· Buffalodevice
80%
All versions

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (4)

Third Party AdvisoryUS Government Resource
Source: [email protected]
https://www.kb.cert.org/vuls/id/914124
ExploitThird Party Advisory
Source: [email protected]
https://www.secpod.com/blog/arcadyan-based-routers-and-modems-under-active-exploitation/
x_refsource_MISCExploitThird Party Advisory
Source: [email protected]
https://www.tenable.com/security/research/tra-2021-13
US Government Resource
Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-20090

SSVC — Action Prioritization

SSVCActiveAutomatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

9.8CRITICALCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-22

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