CVE-2021-20090 Arcadyan Buffalo Firmware: file path flaw
In plain words: The program can be tricked into reading or writing files outside the folder it should stay in. Leaks files such as passwords and settings, or overwrites important ones.
Confirmed exploited by CISA on · US federal patch deadline Nov 17, 2021
What to do
- Install Arcadyan's security update for Buffalo Firmware. If no update exists, follow the vendor's workaround or stop using the product until one ships.
- Patch edge devices first — attackers often start scanning for them within hours of a fix.
- Never expose the device's admin page to the internet.
- After patching a device that was exposed, follow the vendor's compromise checks, end active sessions and change passwords.
Who is affected
Work IT. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.
What's at risk: They face the internet and guard the whole network, so a flaw here can hand attackers a way in — and these devices usually run no antivirus, so break-ins go unnoticed.
The details
- Official name
- Arcadyan Buffalo Firmware Path Traversal Vulnerability
- Product
- Arcadyan Buffalo Firmware
- CISA description
- Arcadyan Buffalo firmware contains a path traversal vulnerability that could allow unauthenticated, remote attackers to bypass authentication and access sensitive information. This vulnerability affects multiple routers across several different vendors.
- Type of flaw
- File path flaw (CWE-22)
- Confirmed exploited
- Nov 3, 2021
- US federal patch deadline
- Nov 17, 2021
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Answering about CVE-2021-20090 ·
Questions about CVE-2021-20090
Is CVE-2021-20090 being exploited?
Yes. CISA added CVE-2021-20090 to its Known Exploited Vulnerabilities catalog on Nov 3, 2021, which means there is reliable evidence of real-world attacks.
How do I fix CVE-2021-20090?
Install Arcadyan's security update for Buffalo Firmware. If no update exists, follow the vendor's workaround or stop using the product until one ships. Patch edge devices first — attackers often start scanning for them within hours of a fix.
Am I affected by CVE-2021-20090?
Only if you use Arcadyan Buffalo Firmware. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.