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CVE-2021-20090

98
FAUCET Score

CVE-2021-20090 is a critical path traversal vulnerability affecting Buffalo WSR-2533DHPL2 (firmware <= 1.02) and WSR-2533DHP3 (firmware <= 1.24) routers, allowing unauthenticated remote attackers to bypass authentication. With a CVSS score of 9.8, this vulnerability is easily exploitable over the network without user interaction, leading to complete compromise of confidentiality, integrity, and availability. It is actively exploited in the wild, as evidenced by its inclusion in CISA's KEV catalog and numerous media reports detailing its use in botnet campaigns. While no Metasploit or ExploitDB modules exist, Nuclei templates are available, and there is significant community discussion and media coverage surrounding this high-risk flaw.

Impacted Technologies

VendorProductVersion(s)CPE
<= 1.02CPE matchmatch criteria
cpe:2.3:o:buffalo:wsr-2533dhpl2-bk_firmware:*:*:*:*:*:*:*:*
<= 1.24CPE matchmatch criteria
cpe:2.3:o:buffalo:wsr-2533dhp3-bk_firmware:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
99.98%
Probability of exploitation in next 30 days
EPSS Percentile
100.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Added to KEV · Nov 3, 2021
Nuclei: CVE-2021-20090 · Aug 10, 2021
This CVE's current EPSS score of 0.9998 is in the 100th percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (5)

asteriskvendor investigatingvia llm_extracted
ciscovendor investigatingvia llm_extracted
mariadbvendor investigatingvia llm_extracted
miniovendor investigatingvia llm_extracted
openrefinevendor investigatingvia llm_extracted

Vendor Advisories (5)

miniollm-minio-6cd8473b0cee6034HIGH

Multiple Vulnerabilities in Buffalo and Arcadyan manufactured routers

Apr 23, 2021
ciscollm-cisco-e7530536477a47c9HIGH

Multiple Vulnerabilities in Buffalo and Arcadyan manufactured routers

Apr 23, 2021
asteriskllm-asterisk-cc6ce2aa3705cde0HIGH

Multiple Vulnerabilities in Buffalo and Arcadyan manufactured routers

Apr 23, 2021
openrefinellm-openrefine-7ef16c669d189abbHIGH

Multiple Vulnerabilities in Buffalo and Arcadyan manufactured routers

Apr 23, 2021
mariadbllm-mariadb-a56c4813c1c993bcHIGH

Multiple Vulnerabilities in Buffalo and Arcadyan manufactured routers

Apr 23, 2021

References

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