CVE-2024-40891Known exploitationPublic exploitNetwork attack vector

Authenticated command execution via unfiltered Telnet commands

Published Feb 4, 2025 · Updated Oct 21, 2025

OS command injection in Zyxel VMG4325-B10A firmware 1.00(AAFR.4)C0_20170615 allows remote authenticated users to execute commands via Telnet. The libcms_cli.so command path accepts utilities such as ping or tftp by prefix alone, then passes the complete unfiltered string to runCommandInShell. Any account reaches the flaw, but Telnet and WAN access are disabled by default; shell metacharacters grant unrestricted command execution when enabled.

CVSS severity8.8
High
EPSS probability21.54%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OS command injection in Zyxel VMG4325-B10A firmware 1.00(AAFR.4)C0_20170615 allows remote authenticated users to execute commands via Telnet. The libcms_cli.so command path accepts utilities such as ping or tftp by prefix alone, then passes the complete unfiltered string to runCommandInShell. Any account reaches the flaw, but Telnet and WAN access are disabled by default; shell metacharacters grant unrestricted command execution when enabled.

The record

CVE
CVE-2024-40891
Published
Feb 4, 2025
Updated
Oct 21, 2025
Vendor
Zyxel Networks
Product
VMG4325-B10A firmware
Classifications
CWE-78, T1059
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 21, 2025Exploitation reportedMirai exploitation of Zyxel CPE devices
  2. Feb 4, 2025CVE publishedPublication date reported by the CVE source.
  3. Feb 11, 2025Exploitation reportedCISA Known Exploited Vulnerabilities catalog listing
  4. Oct 21, 2025Record 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(AAFR.4)C0_20170615

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Zyxel Networks · VMG4325-B10A firmwareversion=<= 1.00(AAFR.4)C0_20170615

Published CVSS scores

8.8Zyxel CNACVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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)
Vectornetwork
Privilegesauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
T1059Command and Scripting Interpreter

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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