CVE-2021-20649Network attack vector

OS command execution via unvalidated update response

Published Feb 12, 2021 · Updated Aug 3, 2024

Improper certificate validation in ELECOM WRC-300FEBK-S allows man-in-the-middle attackers to execute OS commands through firmware update checks. The update-file check accepts a communication response without properly validating the SSL server certificate, allowing substituted response content to drive command execution. Exploitation requires man-in-the-middle control of update-check traffic and use of the nonautomatic update-file check; the consequence is command execution on the router.

CVSS severity4.8
Medium
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in ELECOM WRC-300FEBK-S allows man-in-the-middle attackers to execute OS commands through firmware update checks. The update-file check accepts a communication response without properly validating the SSL server certificate, allowing substituted response content to drive command execution. Exploitation requires man-in-the-middle control of update-check traffic and use of the nonautomatic update-file check; the consequence is command execution on the router.

The record

CVE
CVE-2021-20649
Published
Feb 12, 2021
Updated
Aug 3, 2024
Vendor
ELECOM CO., LTD.
Product
WRC-300FEBK-S
Classifications
CWE-295, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 12, 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

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Is a vulnerable build present?

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

  1. Affected versionversion=WRC-300FEBK-S

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ELECOM CO., LTD. · WRC-300FEBK-Sversion=WRC-300FEBK-S

Published CVSS scores

4.0JPCERT/CCAV:N/AC:H/Au:N/C:P/I:P/A:N
5.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:N
4.8JPCERT/CCCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
4.8NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1557Adversary-in-the-Middle

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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