CVE-2021-35035Network attack vector

Configuration disclosure via missing file permission controls

Published Dec 29, 2021 · Updated Aug 4, 2024

Cleartext storage in Zyxel NBG6604 firmware 1.00(ABIR.8)C0 allows remote authenticated users to read sensitive configuration data. The configuration file lacks proper permission controls, leaving its sensitive contents retrievable in cleartext. High-privilege authentication is required, and the documented impact is limited to confidentiality.

CVSS severity4.9
Medium
EPSS probability0.65%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cleartext storage in Zyxel NBG6604 firmware 1.00(ABIR.8)C0 allows remote authenticated users to read sensitive configuration data. The configuration file lacks proper permission controls, leaving its sensitive contents retrievable in cleartext. High-privilege authentication is required, and the documented impact is limited to confidentiality.

The record

CVE
CVE-2021-35035
Published
Dec 29, 2021
Updated
Aug 4, 2024
Vendor
Zyxel Networks
Product
NBG6604 firmware
Classifications
CWE-312
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Dec 29, 2021CVE 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?

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

  1. Affected versionversion=1.00(ABIR.8)C0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Zyxel Networks · NBG6604 firmwareversion=1.00(ABIR.8)C0

Published CVSS scores

4.9Zyxel CorporationCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
4.0NIST NVDAV:N/AC:L/Au:S/C:P/I:N/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.

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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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-312Cleartext Storage of Sensitive Information

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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