CVE-2021-20090
CriticalExploitedPublic exploitA 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.
Published Apr 29, 2021 · Updated Nov 3, 2025
Key Facts
Patch immediately- CVE-2021-20090 is a critical-severity vulnerability (CVSS 9.8 v3.1) affecting Wsr-2533dhp3-Bk Firmware (Buffalo), Wsr-2533dhpl2-Bk Firmware (Buffalo), Buffalo WSR-2533DHPL2, Buffalo WSR-2533DHP3.
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Aug 6, 2021. Public exploit code is available.
- EPSS estimates a 100% probability of exploitation in the next 30 days.
- Fixed versions are available, including Wsr-2533dhp3-Bk Firmware <=1.24, Wsr-2533dhpl2-Bk Firmware <=1.02, Wsr-2533dhp3-Bk Firmware 1.24.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
9.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
100%
Higher than 99.9% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings
Public exploit code
Available
Proof-of-concept or weaponized module
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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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Nov 3, 2021 | Nov 17, 2021 | Not reported |
| Industry KEV feed | Aug 6, 2021 | Nov 17, 2021 | Not reported |
| CIRCL KEV | Nov 3, 2021 | Nov 17, 2021 | Not reported |
| ENISA EUVD | Nov 3, 2021 | n/a | Not reported |
Required action: Apply updates per vendor instructions.
Affected Products
3 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Wsr-2533dhp3-Bk FirmwareBuffalo | See advisory | 1.24 |
| Wsr-2533dhpl2-Bk FirmwareBuffalo | See advisory | 1.02 |
| Buffalo WSR-2533DHPL2, Buffalo WSR-2533DHP3 | >= WSR-2533DHPL2 <=1.02, WSR-2533DHP3 <= 1.24 | n/a |
Patched Releases
Wsr-2533dhp3-Bk Firmware
<=1.24
Wsr-2533dhpl2-Bk Firmware
<=1.02
Timeline
Publicly disclosed
Apr 29, 2021
Added to Industry KEV feed
Aug 6, 2021
Added to CISA KEV
Nov 3, 2021
Added to CIRCL KEV
Nov 3, 2021
Added to ENISA EUVD
Nov 3, 2021
Last updated
Nov 3, 2025
Weakness Type
- CWE-22 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
References
- advisoryVU#914124
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
FAQ
Common Questions.
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.
Affected: Wsr-2533dhp3-Bk Firmware (Buffalo); Wsr-2533dhpl2-Bk Firmware (Buffalo); Buffalo WSR-2533DHPL2, Buffalo WSR-2533DHP3 versions >= WSR-2533DHPL2 <=1.02, WSR-2533DHP3 <= 1.24. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Aug 6, 2021.
Yes. It was added on Nov 3, 2021 with a federal remediation due date of Nov 17, 2021.
Public exploit code is available.
Fixed versions are available, including Wsr-2533dhp3-Bk Firmware <=1.24, Wsr-2533dhpl2-Bk Firmware <=1.02, Wsr-2533dhp3-Bk Firmware 1.24.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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