How to check if you are exposed to CVE-2023-28771
- Find every Zyxel Multiple Firewalls system you or your clients run, including ones exposed to the internet. Those come first: CISA only lists flaws attackers are already using.
- Compare each version with the fixed versions in the vendor advisory below. Where no fix exists yet, apply the vendor’s mitigation or take the system off the internet.
- Run a credentialed vulnerability scan to catch the systems you missed, then check that the next scan no longer reports CVE-2023-28771.
US federal agencies had to fix this by 2023-06-21. Everyone else should treat that deadline as a guide: if it has passed, this is overdue.
Timeline
- · Added to CISA's Known Exploited Vulnerabilities catalog
- · Fix-by date for US federal agencies, passed 1,229 days ago
Vendor advisories and fixes
Weakness type
More exploited Zyxel vulnerabilities
CISA lists 13 exploited Zyxel vulnerabilities. The closest matches:
- CVE-2024-11667Zyxel Multiple Firewalls Path Traversal VulnerabilityAdded 2024-12-03
- CVE-2023-33010Zyxel Multiple Firewalls Buffer Overflow VulnerabilityAdded 2023-06-05
- CVE-2023-33009Zyxel Multiple Firewalls Buffer Overflow VulnerabilityAdded 2023-06-05
- CVE-2022-30525Zyxel Multiple Firewalls OS Command Injection VulnerabilityAdded 2022-05-16
- CVE-2026-7273Zyxel GS1900 Series Switches Stack-Based Buffer Overflow VulnerabilityAdded 2026-09-21
- CVE-2024-40891Zyxel DSL CPE OS Command Injection VulnerabilityAdded 2025-02-11
- CVE-2024-40890Zyxel DSL CPE OS Command Injection VulnerabilityAdded 2025-02-11
- CVE-2017-6884Zyxel EMG2926 Routers Command Injection VulnerabilityAdded 2023-09-18
Keep going
Sources: CISA Known Exploited Vulnerabilities catalog (version 2026.10.30); EPSS data from FIRST.org; CVSS and descriptions from the NIST National Vulnerability Database. Checked 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.