CyberSecBulletin
CVE-2023-28767NVD status: Modified

ATP series firmware: Improper Neutralization of Special Elements used in an OS Command

Published Updated By the CyberSecBulletin desk

CVE-2023-28767 is a high-severity improper neutralization of special elements used in an OS command vulnerability in ATP series firmware from Zyxel, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited from the same local network by an unauthenticated attacker, without any action from a user. Affected ATP series firmware versions: 5.10 through 5.36. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.4% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Usg 2200-vpn Firmware to 5.37 or a later version.
  2. Update Usg Flex 100 Firmware to 5.37 or a later version.
  3. Update Usg Flex 100w Firmware to 5.37 or a later version.
  4. Read the advisory on zyxel.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
ZyxelATP series firmware5.10 through 5.36Not stated
ZyxelUSG FLEX series firmware5.00 through 5.36; 5.0.0 through 5.36Not stated
ZyxelUSG FLEX 50(W) series firmware5.10 through 5.36Not stated
ZyxelUSG20(W)-VPN series firmware5.10 through 5.36Not stated
ZyxelVPN series firmware5.00 through 5.36Not stated
ZyxelUsg 2200-vpn Firmware5.00 up to, but not including, 5.375.37
ZyxelUsg Flex 100 Firmware5.00 up to, but not including, 5.375.37
ZyxelUsg Flex 100w Firmware5.00 up to, but not including, 5.375.37
ZyxelUsg Flex 200 Firmware5.00 up to, but not including, 5.375.37
ZyxelUsg Flex 50 Firmware5.00 up to, but not including, 5.375.37
ZyxelUsg Flex 500 Firmware5.00 up to, but not including, 5.375.37
ZyxelUsg Flex 50w Firmware5.00 up to, but not including, 5.375.37
ZyxelUsg Flex 700 Firmware5.00 up to, but not including, 5.375.37
ZyxelZywall Vpn100 Firmware5.00 up to, but not including, 5.375.37
ZyxelZywall Vpn2s Firmware5.00 up to, but not including, 5.375.37
ZyxelZywall Vpn300 Firmware5.00 up to, but not including, 5.375.37
ZyxelZywall Vpn50 Firmware5.00 up to, but not including, 5.375.37
ZyxelZywall VPN 100 Firmware5.00 up to, but not including, 5.375.37
ZyxelZywall VPN 300 Firmware5.00 up to, but not including, 5.375.37
ZyxelZywall VPN 50 Firmware5.00 up to, but not including, 5.375.37
ZyxelUsg 20w-vpn Firmware5.10 up to, but not including, 5.375.37
ZyxelZywall Atp100 Firmware5.10 up to, but not including, 5.375.37
ZyxelZywall Atp100w Firmware5.10 up to, but not including, 5.375.37
ZyxelZywall Atp200 Firmware5.10 up to, but not including, 5.375.37
ZyxelZywall Atp500 Firmware5.10 up to, but not including, 5.375.37

Version data comes from the organisation that assigned the CVE; 2 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
AdjacentThe attacker must be on the same local network segment.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
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:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (zyxel.com.tw).

Official description

The configuration parser fails to sanitize user-controlled input in the Zyxel ATP series firmware versions 5.10 through 5.36, USG FLEX series firmware versions 5.00 through 5.36, USG FLEX 50(W) series firmware versions 5.10 through 5.36, USG20(W)-VPN series firmware versions 5.10 through 5.36, and VPN series firmware versions 5.00 through 5.36. An unauthenticated, LAN-based attacker could leverage the vulnerability to inject some operating system (OS) commands into the device configuration data on an affected device when the cloud management mode is enabled.

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: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in ATP series firmware

All ATP series firmware vulnerabilities

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

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