CVE-2021-20090 — Arcadyan Buffalo Firmware Path Traversal Vulnerability

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.

01What is this vulnerability?

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.

02Affected products

Vendor	Product	Versions
n	a / Buffalo WSR	2533DHPL2, Buffalo WSR-2533DHP3 — WSR-2533DHPL2 <=1.02, WSR-2533DHP3 <= 1.24

03Active exploitation status

Yes — actively exploited. Added to the CISA KEV catalog on 2021-11-03. Ransomware use: Unknown.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Open the Sigma generator with a pre-filled prompt for this CVE to draft a starting detection in your stack of choice:

Open in Sigma generator →

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2021-04-29T00:00:00.000Z
• Last modified: 2025-10-21T23:25:47.628Z
• Added to CISA KEV: 2021-11-03
• BOD 22-01 due: 2021-11-17

09References

• www.tenable.com — https://www.tenable.com/security/research/tra-2021-13
• www.kb.cert.org — https://www.kb.cert.org/vuls/id/914124
• www.secpod.com — https://www.secpod.com/blog/arcadyan-based-routers-and-modems-under-active-explo…