ATP series firmware: Improper Neutralization of Special Elements used in an OS Command
CVE-2023-34141 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 8.0 out of 10. It can be exploited from the same local network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. Affected ATP series firmware versions: 5.00 through 5.36 Patch 2. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.68% chance of exploitation within 30 days, higher than 53% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Usg 20w-vpn Firmware to 5.37 or a later version.
- Update Usg 2200-vpn Firmware to 5.37 or a later version.
- Update Usg Flex 100 Firmware to 5.37 or a later version.
- Read the advisory on zyxel.com for workarounds and exact fixed builds.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Zyxel | ATP series firmware | 5.00 through 5.36 Patch 2 | Not stated |
| Zyxel | USG FLEX series firmware | 5.00 through 5.36 Patch 2 | Not stated |
| Zyxel | USG FLEX 50(W) series firmware | 5.00 through 5.36 Patch 2 | Not stated |
| Zyxel | USG20(W)-VPN series firmware | 5.00 through 5.36 Patch 2 | Not stated |
| Zyxel | VPN series firmware | 5.00 through 5.36 Patch 2 | Not stated |
| Zyxel | NXC2500 firmware | 6.10(AAIG.0) through 6.10(AAIG.3) | Not stated |
| Zyxel | NXC5500 firmware | 6.10(AAOS.0) through 6.10(AAOS.4) | Not stated |
| Zyxel | atp | 5.00 through 5.36_patch-2 | Not stated |
| Zyxel | usg_flex | 5.00 through 5.36_patch-2 | Not stated |
| Zyxel | usg_flex_50w_firmware | 5.00 through 5.36_patch-2 | Not stated |
| Zyxel | usg20w-vpn_firmware | 5.00 through 5.36_patch-2 | Not stated |
| Zyxel | vpn_firmware | 5.00 through 5.36_patch-2 | Not stated |
| Zyxel | Usg 20w-vpn Firmware | 5.00 up to, but not including, 5.37 | 5.37 |
| Zyxel | Usg 2200-vpn Firmware | 5.00 up to, but not including, 5.37 | 5.37 |
| Zyxel | Usg Flex 100 Firmware | 5.00 up to, but not including, 5.37 | 5.37 |
| Zyxel | Usg Flex 100w Firmware | 5.00 up to, but not including, 5.37 | 5.37 |
| Zyxel | Usg Flex 200 Firmware | 5.00 up to, but not including, 5.37 | 5.37 |
| Zyxel | Usg Flex 50 Firmware | 5.00 up to, but not including, 5.37 | 5.37 |
| Zyxel | Usg Flex 500 Firmware | 5.00 up to, but not including, 5.37 | 5.37 |
| Zyxel | Usg Flex 700 Firmware | 5.00 up to, but not including, 5.37 | 5.37 |
| Zyxel | Zywall Atp100 Firmware | 5.00 up to, but not including, 5.37 | 5.37 |
| Zyxel | Zywall Atp100w Firmware | 5.00 up to, but not including, 5.37 | 5.37 |
| Zyxel | Zywall Atp200 Firmware | 5.00 up to, but not including, 5.37 | 5.37 |
| Zyxel | Zywall Atp500 Firmware | 5.00 up to, but not including, 5.37 | 5.37 |
| Zyxel | Zywall Atp700 Firmware | 5.00 up to, but not including, 5.37 | 5.37 |
Version data comes from the organisation that assigned the CVE; 8 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
- RequiredA user must take an action such as opening a file or link.
- 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:R/S:U/C:H/I:H/A:H. Scored by CNA (zyxel.com.tw).
Official description
A command injection vulnerability in the access point (AP) management feature of the Zyxel ATP series firmware versions 5.00 through 5.36 Patch 2, USG FLEX series firmware versions 5.00 through 5.36 Patch 2, USG FLEX 50(W) series firmware versions 5.00 through 5.36 Patch 2, USG20(W)-VPN series firmware versions 5.00 through 5.36 Patch 2, VPN series firmware versions 5.00 through 5.36 Patch 2, NXC2500 firmware versions 6.10(AAIG.0) through 6.10(AAIG.3), and NXC5500 firmware versions 6.10(AAOS.0) through 6.10(AAOS.4), could allow an unauthenticated, LAN-based attacker to execute some OS commands on an affected device if the attacker could trick an authorized administrator to add their IP address to the managed AP list in advance.
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
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other vulnerabilities in ATP series firmware
- 7.2 High severity
- 7.2 High severity
- 8.1 High severity
- 7.2 High severity
- 9.8 Critical severity
Zyxel Multiple Firewalls Path Traversal Exploited
- 7.2 High severity
Recent Improper Neutralization of Special Elements used in an OS Command vulnerabilities
- 8.8 High severity
- 8.0 High severity
- 8.8 High severity
- 8.8 High severity
- 9.8 Critical severity
- 8.0 High severity
Spotted an error? Tell us.