A path traversal vulnerability in the web interfaces of Buffalo WSR-2533DHPL2 firmware version <= 1.02 and WSR-2533DHP3 firmware version <=…

published 2021-04-29 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-7547

cvss: 9.8; version 3.1, CNA
cisa kev: Exploited; added 2021-11-03
epss: 100.0%; EPSS 100.0% chance of exploitation in 30 days, percentile 99.9%
public exploits: 0; none known, plus a Nuclei check

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.

Patch / fix

cisa required action Apply updates per vendor instructions.

Timeline

2021-04-29 Published
2021-11-03 Added to CISA KEV
2021-11-17 CISA patch deadline
2025-02-06 CISA SSVC: exploitation active

Known exploited

Added: 5 y ago (2021-11-03)
Patch by: 2021-11-17 (4 y ago)
Ransomware: Not known
Required action: Apply updates per vendor instructions.
Vendor, product: Arcadyan, Buffalo Firmware
CISA name: Arcadyan Buffalo Firmware Path Traversal Vulnerability

CISA SSVC

Exploitation: Active, exploited in the wild
Automatable: yes
Technical impact: total
Assessed: 21 mo ago (2025-02-06)

Exploit prediction

99.98% chance of exploitation in the next 30 days, higher than 99.9% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

Nuclei template Buffalo WSR-2533DHPL2 - Path Traversal nuclei detection template
tenable.com https://www.tenable.com/security/research/tra-2021-13 referenced PoC, tagged "exploit" by a source, unverified
secpod.com https://www.secpod.com/blog/arcadyan-based-routers-and-modems-under-active-exploitation/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD	2.0	7.5	AV:N/AC:L/Au:N/C:P/I:P/A:P

Affected products

n/a Buffalo WSR-2533DHPL2, Buffalo WSR-2533DHP3

Classification

Weakness

CWE-22 Improper Limitation of a Pathname to a Restricted Directory

References

tenable.com /security/research/tra-2021-13
exploit, third-party-advisory
secpod.com /blog/arcadyan-based-routers-and-modems-under-active-exploitation/
exploit, third-party-advisory
kb.cert.org /vuls/id/914124
third-party-advisory, us-government-resource
cisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-20090
government-resource, us-government-resource

Sources

CVE List CVE-2021-20090
NVD CVE-2021-20090

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary