CVE-2021-20852

Authenticated OS command execution via buffer overflow

Published Dec 1, 2021 · Updated Aug 3, 2024

Buffer overflow in ELECOM WRH-733GBK and WRH-733GWH firmware 1.02.9 and earlier allows remote authenticated users to execute OS commands from the LAN. ELECOM and JVN identify a buffer overflow but do not disclose the affected firmware component, input field, or unchecked copy operation. Access to the management screen with administrator privileges from an adjacent network is required, and successful exploitation runs arbitrary commands on the router.

CVSS severity6.8
Medium
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer overflow in ELECOM WRH-733GBK and WRH-733GWH firmware 1.02.9 and earlier allows remote authenticated users to execute OS commands from the LAN. ELECOM and JVN identify a buffer overflow but do not disclose the affected firmware component, input field, or unchecked copy operation. Access to the management screen with administrator privileges from an adjacent network is required, and successful exploitation runs arbitrary commands on the router.

The record

CVE
CVE-2021-20852
Published
Dec 1, 2021
Updated
Aug 3, 2024
Vendor
ELECOM CO., LTD.
Product
ELECOM LAN Routers
Classifications
CWE-121, CWE-120
Attack vector
adjacent
Privileges
admin

Timeline

How it unfolded

  1. Dec 1, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=WRH-733GBK firmware v1.02.9 and prior and WRH-733GWH firmware v1.02.9 and prior

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesadmin

What is affected?

ELECOM CO., LTD. · ELECOM LAN Routersversion=WRH-733GBK firmware v1.02.9 and prior and WRH-733GWH firmware v1.02.9 and prior

Published CVSS scores

5.2JPCERT/CC and IPAAV:A/AC:L/Au:S/C:P/I:P/A:P
6.8NIST NVDCVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
6.8JPCERT/CC and IPACVSS:3.0/AV:A/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-121Stack-based Buffer Overflow
CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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