Full Report
Zyxel security advisory (AV26-092)
Analysis Summary
As a vulnerability research specialist, here is the summary of the Zyxel security advisory AV26-092 based on the provided context:
# Vulnerability: Post-Authentication Command Injection in ZLD DDNS CLI
## CVE Details
*Note: The provided context does not specify the CVE ID or CVSS score. These fields remain placeholder.*
- CVE ID: [TBD]
- CVSS Score: [TBD] ([TBD])
- CWE: [TBD, likely related to Command Injection]
## Affected Systems
- Products: ATP series, USG FLEX series, USG FLEX 50(W), USG20(W)-VPN
- Versions: ZLD V5.35 up to and including V5.41
- Configurations: Affects the DDNS configuration CLI command. Requires authentication.
## Vulnerability Description
The vulnerability is a post-authentication command injection flaw residing within the Dynamic Domain Name System (DDNS) configuration command-line interface (CLI) used on affected Zyxel ZLD firewalls. An authenticated attacker can leverage this flaw to inject and execute arbitrary system commands, leading to potential system compromise.
## Exploitation
- Status: Information regarding active exploitation is not provided in the context. Assume **PoC available** if detailed vendor advisories mention it.
- Complexity: Likely **Medium**, as it requires prior authentication.
- Attack Vector: **Adjacent** or **Local** (if an authenticated management interface is accessible).
## Impact
*Note: Specific impact ratings are inferred based on command injection severity, as the context does not provide specific metrics.*
- Confidentiality: High (Risk of reading sensitive system files or configurations)
- Integrity: High (Risk of modifying system configurations or installing persistent backdoors)
- Availability: High (Risk of system denial of service or complete compromise)
## Remediation
### Patches
*Note: Specific fixed versions are not detailed in the snippet, but applying updates is required.*
- Users must apply updates released by Zyxel addressing versions V5.35 to V5.41 on ATP, USG FLEX, USG FLEX 50(W), and USG20(W)-VPN devices. **Check the vendor advisory for the precise patched versions.**
### Workarounds
- Since the vulnerability requires authentication, restrict management access to the DDNS CLI command to the absolute minimum necessary users or trusted IP addresses.
## Detection
- Indicators of Compromise (IOCs): Look for unusual command execution or process spawning originating from the firewall's DDNS configuration handling routines within system logs immediately following authenticated administrative actions.
- Detection Methods and Tools: Review firewall command history logs for evidence of appended or malformed input intended for DDNS settings.
## References
- Zyxel security advisory (Post-Authentication Command Injection DDNS CLI): hxxps://www.zyxel[.]com/global/en/support/security-advisories/zyxel-security-advisory-for-post-authentication-command-injection-vulnerability-in-the-ddns-configuration-cli-command-of-zld-firewalls-02-05-2026
- Zyxel Advisories Portal: hxxps://www.zyxel[.]com/global/en/support/security-advisories