CVE-2021-20090A path traversal vulnerability in the web interfaces of Buffalo WSR-2533DHPL2 firmware version <= 1.02 and WSR-2533DHP3 firmware version…
- 9.8CriticalCVSS base score
- 100.0%Exploitation in 30 daysEPSS · top 0.1% of all CVEs
- YesKnown exploitedin CISA's KEV since 3 Nov 2021
- 1Public exploitsMetasploit, Nuclei and Exploit-DB
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.
Exploited in the wild
CISA lists this vulnerability in its Known Exploited Vulnerabilities catalog as Arcadyan Buffalo Firmware Path Traversal Vulnerability.
- Added
- 3 Nov 2021
- Fix due (US federal)
- 17 Nov 2021
- Used by ransomware
- Not known
Apply updates per vendor instructions.
ENISA's EU Vulnerability Database lists it as exploited, from CISA's KEV, since 3 Nov 2021.
Public exploit
An exploit or proof of concept is public: anyone can try it against an unpatched system. The public collections list a Nuclei template for it. CISA's SSVC rates its exploitation: it is being exploited.
Show the exploits1
Nuclei templates1 template
- Buffalo WSR-2533DHPL2 - Path Traversal (Nuclei template) (opens in a new tab)
http/cves/2021/CVE-2021-20090.yamlSeverity critical
Modules, templates and exploits as listed by the Metasploit Framework (BSD-3-Clause), ProjectDiscovery's Nuclei templates (MIT) and the Exploit Database (GPLv2), read once a day. Where the data comes from
Timeline
ID reserved
By tenable
- 4 months later
· 4 months later
Published
- 6 months later
· 6 months later
Added to CISA KEV
Known exploited in the wild
- 4 years later
· 4 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| CISA-ADPADP (enrichment) | 3.1 | Critical9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| NVDNVD · Analyzed | 3.1 | Critical9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 100.0% · top 0.1% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: active · Automatable: yes · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.8.
Affected products
Buffalo WSR-2533DHPL2, Buffalo WSR-2533DHP3
- affected WSR-2533DHPL2 <=1.02, WSR-2533DHP3 <= 1.24
References
References4
- https://www.tenable.com/security/research/tra-2021-13 (opens in a new tab)x_transferred
- VU#914124 (opens in a new tab)third-party-advisoryx_transferred
- https://www.secpod.com/blog/arcadyan-based-routers-and-modems-under-active-exploitation/ (opens in a new tab)x_transferred
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-20090 (opens in a new tab)government-resource
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- CISA KEV catalog (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2021-7547 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2021-20090)Record last updated .