CVE-2021-20161

Root shell access via unauthenticated UART console

Published Dec 30, 2021 · Updated Aug 3, 2024

Missing authentication on the TRENDnet TEW-827DRU 2.08B01 UART allows physically proximate attackers to obtain a root shell. The UART serial console accepts a physical serial connection and starts a root shell without requesting a username or password. Exploitation requires physical access to the router and grants full control of its firmware, configuration, and network functions.

CVSS severity6.8
Medium
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing authentication on the TRENDnet TEW-827DRU 2.08B01 UART allows physically proximate attackers to obtain a root shell. The UART serial console accepts a physical serial connection and starts a root shell without requesting a username or password. Exploitation requires physical access to the router and grants full control of its firmware, configuration, and network functions.

The record

CVE
CVE-2021-20161
Published
Dec 30, 2021
Updated
Aug 3, 2024
Vendor
TRENDnet
Product
TEW-827DRU
Classifications
CWE-287, CWE-306, T1059
Attack vector
physical
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 30, 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=2.08B01

What conditions does exploitation require?

Attack vectorphysical
Required privilegesunauthenticated

What is affected?

TRENDnet · TEW-827DRUversion=2.08B01

Published CVSS scores

6.8TenableCVSS:3.0/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
6.8NIST NVDCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.2NIST NVDAV:L/AC:L/Au:N/C:C/I:C/A:C

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)
Vectorphysical
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
CWE-306Missing Authentication for Critical Function
T1059Command and Scripting Interpreter

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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