CVE-2021-20090 — Wsr-2533dhp3-Bk Firmware
CRITICALCVE-2021-20090 is a critical-severity (CVSS 9.8) Path Traversal vulnerability in buffalo wsr-2533dhp3-bk firmware. It is in CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.
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…
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2021-11-03. Federal agencies were required to remediate by 2021-11-17.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2021-20090.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-20090 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).
Where this sits among everything scored
Of 395,249 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.
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.
Affected Products
wsr-2533dhp3-bk firmwarebuffalowsr-2533dhpl2-bk firmwarebuffaloResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
A path traversal vulnerability in the web interfaces of Buffalo WSR-2533…
A path traversal vulnerability in the web interfaces of Buffalo WSR-2533…
A path traversal vulnerability in the web interfaces of Buffalo WSR-2533…
A path traversal vulnerability in the web interfaces of Buffalo WSR-2533…
Detection & mitigation playbook
Vendor / applianceDetect
Inventory every buffalo wsr-2533dhp3-bk firmware deployment and check each version against the affected-products list above.
Remediation status
No patch has shipped for CVE-2021-20090 yet — track the buffalo wsr-2533dhp3-bk firmware advisory for a fixed release and apply the workarounds below in the meantime.
Mitigate without a patch
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
How to detect CVE-2021-20090
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2021-20090 -u https://target- Template
- Buffalo WSR-2533DHPL2 - Path Traversal
- Severity
- critical
- Impact
- An attacker can exploit this vulnerability to read sensitive files, such as configuration files, credentials, or other sensitive information.
- Remediation
- Apply the latest firmware update provided by Buffalo to fix the path traversal vulnerability.
Template by ProjectDiscovery nuclei-templates (gy741), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2021-20090 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.