HOMEVULNERABILITIESCVE-2021-20716
CRITICAL

CVE-2021-20716

NVD-CWE-OtherPublished: April 28, 2021· Updated: Jun 17, 2026

9.8
CVSS v3.1

Official Description

Hidden functionality in multiple Buffalo network devices (BHR-4RV firmware Ver.2.55 and prior, FS-G54 firmware Ver.2.04 and prior, WBR2-B11 firmware Ver.2.32 and prior, WBR2-G54 firmware Ver.2.32 and prior, WBR2-G54-KD firmware Ver.2.32 and prior, WBR-B11 firmware Ver.2.23 and prior, WBR-G54 firmware Ver.2.23 and prior, WBR-G54L firmware Ver.2.20 and prior, WHR2-A54G54 firmware Ver.2.25 and prior, WHR2-G54 firmware Ver.2.23 and prior, WHR2-G54V firmware Ver.2.55 and prior, WHR3-AG54 firmware Ver.2.23 and prior, WHR-G54 firmware Ver.2.16 and prior, WHR-G54-NF firmware Ver.2.10 and prior, WLA2-G54 firmware Ver.2.24 and prior, WLA2-G54C firmware Ver.2.24 and prior, WLA-B11 firmware Ver.2.20 and prior, WLA-G54 firmware Ver.2.20 and prior, WLA-G54C firmware Ver.2.20 and prior, WLAH-A54G54 firmware Ver.2.54 and prior, WLAH-AM54G54 firmware Ver.2.54 and prior, WLAH-G54 firmware Ver.2.54 and prior, WLI2-TX1-AG54 firmware Ver.2.53 and prior, WLI2-TX1-AMG54 firmware Ver.2.53 and prior, WLI2-TX1-G54 firmware Ver.2.20 and prior, WLI3-TX1-AMG54 firmware Ver.2.53 and prior, WLI3-TX1-G54 firmware Ver.2.53 and prior, WLI-T1-B11 firmware Ver.2.20 and prior, WLI-TX1-G54 firmware Ver.2.20 and prior, WVR-G54-NF firmware Ver.2.02 and prior, WZR-G108 firmware Ver.2.41 and prior, WZR-G54 firmware Ver.2.41 and prior, WZR-HP-G54 firmware Ver.2.41 and prior, WZR-RS-G54 firmware Ver.2.55 and prior, and WZR-RS-G54HP firmware Ver.2.55 and prior) allows a remote attacker to enable the debug option and to execute arbitrary code or OS commands, change the configuration, and cause a denial of service (DoS) condition.

NVD Source

Technical Analysis

CVE-2021-20716 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

buffalo70 product(s)
bhr-4rv firmwarebhr-4rvfs-g54 firmwarefs-g54wbr2-b11 firmwarewbr2-b11wbr2-g54 firmwarewbr2-g54wbr2-g54-kd firmwarewbr2-g54-kdwbr-b11 firmwarewbr-b11+58
Source: NVD CPE · 70 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttps://jvn.jp/en/vu/JVNVU90274525/index.html
ADVISORYhttps://www.buffalo.jp/news/detail/20210427-02.html
ADVISORYhttps://jvn.jp/en/vu/JVNVU90274525/index.html
ADVISORYhttps://www.buffalo.jp/news/detail/20210427-02.html

All References (4)

→
https://jvn.jp/en/vu/JVNVU90274525/index.htmlThird Party Advisory
→
https://www.buffalo.jp/news/detail/20210427-02.htmlVendor Advisory
→
https://jvn.jp/en/vu/JVNVU90274525/index.htmlThird Party Advisory
→
https://www.buffalo.jp/news/detail/20210427-02.htmlVendor Advisory

Quick Facts

CVE IDCVE-2021-20716
CVSS Score9.8 / 10
SeverityCRITICAL
WeaknessNVD-CWE-Other
CISA KEVNo
Affected1 vendor(s)
PublishedApr 28, 2021

Related CVEs (NVD-CWE-Other)

CVE-1999-0754
10.0
CVE-2001-1080
10.0
CVE-1999-0822
10.0
CVE-2001-0555
10.0
CVE-2000-0032
10.0
CVE-2005-1449
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-20716 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
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