CyberSecBulletin
CVE-2024-40890Exploited in the wildNVD status: Analyzed

Zyxel DSL CPE OS Command Injection

Published Updated By the CyberSecBulletin desk

CVE-2024-40890 is a high-severity improper neutralization of special elements used in an OS command vulnerability in VMG4325-B10A firmware from Zyxel, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected VMG4325-B10A firmware versions: <= 1.00(AAFR.4)C0_20170615. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on February 11, 2025, which means attacks have been observed in the wild.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Check which version of VMG4325-B10A firmware you run against the affected versions below, and install the vendor's latest release.
  2. CISA's required action: The impacted product could be end-of-life (EoL) and/or end-of-service (EoS). Users should discontinue product utilization if a current mitigation is unavailable.
  3. Read the advisory on zyxel.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
ZyxelVMG4325-B10A firmware<= 1.00(AAFR.4)C0_20170615Not stated
ZyxelVmg1312-b10a FirmwareNot specified in the recordNot stated
ZyxelVmg1312-b10b FirmwareNot specified in the recordNot stated
ZyxelVmg1312-b10e FirmwareNot specified in the recordNot stated
ZyxelVmg3312-b10a FirmwareNot specified in the recordNot stated
ZyxelVmg3313-b10a FirmwareNot specified in the recordNot stated
ZyxelVmg3926-b10b FirmwareNot specified in the recordNot stated
ZyxelVmg4380-b10a FirmwareNot specified in the recordNot stated
ZyxelVmg8324-b10a FirmwareNot specified in the recordNot stated
ZyxelVmg8924-b10a FirmwareNot specified in the recordNot stated
ZyxelSbg3300-n000 FirmwareNot specified in the recordNot stated
ZyxelSbg3300-nb00 FirmwareNot specified in the recordNot stated
ZyxelSbg3500-n000 FirmwareNot specified in the recordNot stated
ZyxelSbg3500-nb00 FirmwareNot specified in the recordNot stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (zyxel.com.tw).

Official description

**UNSUPPORTED WHEN ASSIGNED** A post-authentication command injection vulnerability in the CGI program of the legacy DSL CPE Zyxel VMG4325-B10A firmware version 1.00(AAFR.4)C0_20170615 could allow an authenticated attacker to execute operating system (OS) commands on an affected device by sending a crafted HTTP POST request.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Neutralization of Special Elements used in an OS Command

The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command before it is sent to a downstream component.

How developers prevent this class of flaw

  • If at all possible, use library calls rather than external processes to recreate the desired functionality.
  • For any data that will be used to generate a command to be executed, keep as much of that data out of external control as possible. For example, in web applications, this may require storing the data locally in the session's state instead of sending it out to the client in a hidden form field.
  • For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

More Improper Neutralization of Special Elements used in an OS Command vulnerabilities (CWE-78)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
  3. Added to CISA's Known Exploited Vulnerabilities catalogue.
  4. Deadline for US federal agencies to remediate, set by CISA.
  5. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Other vulnerabilities in VMG4325-B10A firmware

All VMG4325-B10A firmware vulnerabilities

Recent Improper Neutralization of Special Elements used in an OS Command vulnerabilities

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