CVE-2021-46559Public exploitNetwork attack vector

Arbitrary code installation via replaceable firmware CRC

Published Jan 26, 2022 · Updated Aug 4, 2024

Improper firmware validation in Moxa TN-5900 firmware 3.1 and earlier allows remote authenticated users to install arbitrary code. The firmware-upload check accepts a simple additive checksum stored as a replaceable CRC value in the image header rather than a cryptographic signature. Access to the management interface and successful authentication are required; a crafted accepted image can persist attacker-supplied code on the router.

CVSS severityUnavailable
Unscored
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

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Summary

What happened

Improper firmware validation in Moxa TN-5900 firmware 3.1 and earlier allows remote authenticated users to install arbitrary code. The firmware-upload check accepts a simple additive checksum stored as a replaceable CRC value in the image header rather than a cryptographic signature. Access to the management interface and successful authentication are required; a crafted accepted image can persist attacker-supplied code on the router.

The record

CVE
CVE-2021-46559
Published
Jan 26, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-354, T1601.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 26, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

No CVSS assessment is available in this record.

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.

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No observations available

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

Weakness, pattern, technique

CWE-354Improper Validation of Integrity Check Value
T1601.001System Firmware

Public exploit references

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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