CVE-2021-20090

Arcadyan Buffalo Firmware Path Traversal

9.8 CRITICALActively exploited (CISA KEV)Public exploitEPSS 100.0%

Published29 Apr 2021
Added to CISA KEV3 Nov 2021
Remediation due17 Nov 2021

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.

CVSS 3.1 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Buffalo Wsr-2533dhp3-bk Firmware≤ 1.24

Buffalo Wsr-2533dhpl2-bk Firmware≤ 1.02

Remediation

No fixed version is recorded in the NVD data. Check the vendor advisory for the latest guidance.

References

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-20090US Government Resource
https://www.kb.cert.org/vuls/id/914124Third Party AdvisoryUS Government Resource
https://www.secpod.com/blog/arcadyan-based-routers-and-modems-under-active-exploitation/ExploitThird Party Advisory
https://www.tenable.com/security/research/tra-2021-13ExploitThird Party Advisory

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2021-20090 being actively exploited?

Yes. CVE-2021-20090 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 3 Nov 2021.

How severe is CVE-2021-20090?

CVE-2021-20090 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 100.0% probability of exploitation.

Which products are affected by CVE-2021-20090?

Affected products include Buffalo Wsr-2533dhp3-bk Firmware, Buffalo Wsr-2533dhpl2-bk Firmware.

How do I fix CVE-2021-20090?

Apply the vendor's patch or advisory guidance, then verify no affected versions remain across your devices.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2021-20090 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, a risk for it never ranks below high, and the update that fixes it moves to the Emergency patch lane. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.