CVE-2021-35031

Authenticated command execution via GUI TFTP client

Published Dec 28, 2021 · Updated Aug 4, 2024

OS command injection in Zyxel GS1900, XGS1210, and XGS1250 switch firmware allows remote authenticated users to execute commands via the LAN GUI. The vendor identifies the TFTP client as the vulnerable locus but has not disclosed which GUI field reaches an OS command or how input is neutralized. Reachability requires authenticated access from the device's LAN, after which injected commands run on the switch operating system.

CVSS severity8.0
High
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OS command injection in Zyxel GS1900, XGS1210, and XGS1250 switch firmware allows remote authenticated users to execute commands via the LAN GUI. The vendor identifies the TFTP client as the vulnerable locus but has not disclosed which GUI field reaches an OS command or how input is neutralized. Reachability requires authenticated access from the device's LAN, after which injected commands run on the switch operating system.

The record

CVE
CVE-2021-35031
Published
Dec 28, 2021
Updated
Aug 4, 2024
Vendor
Zyxel Networks
Product
GS1900 Series Firmware
Classifications
CWE-78, T1059
Attack vector
adjacent
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 28, 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=2.60

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesauthenticated

What is affected?

Zyxel Networks · GS1900 Series Firmwareversion=2.60
Zyxel Networks · XGS1210-12 Firmwareversion=1.00(ABTY.4)C0
Zyxel Networks · XGS1250-12 Firmwareversion=1.00(ABWE.0)C0

Published CVSS scores

8.0NIST NVDCVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
6.8Zyxel CorporationCVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
7.7NIST NVDAV:A/AC:L/Au:S/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)
Vectoradjacent
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
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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