CVE-2021-20090 on CISA KEV

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 CISA says about 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.

02Required action — verbatim from CISA

Apply updates per vendor instructions.

03Notes & references

• 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…

04SARA's analyst layer — why this matters

This vulnerability is currently on the CISA KEV list, which CISA only adds CVEs to when there is reliable evidence of active exploitation in the wild. For federal civilian agencies, BOD 22-01 requires remediation by the due date above. For everyone else, KEV is the strongest "patch immediately" signal you can get from public threat intel.

05Affected products (summary)

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

06Detection

Open the Sigma generator with a pre-filled prompt for this CVE to draft a starting detection:

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