Threats / Zyxel / CVE-2023-28771
CVE-2023-28771
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Zyxel Multiple Firewalls vulnerability
Zyxel firewalls contain an OS command injection vulnerability in error message handling, allowing unauthenticated remote code execution via crafted packets.
Verdict
Today item — known-exploited.
Unauthenticated attackers can execute arbitrary OS commands on affected Zyxel firewalls by exploiting improper error handling. The high EPSS score and active exploitation in the wild indicate immediate risk to exposed devices.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
295 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2023-05-31).
Probability (EPSS)
EPSS 0.99284 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Zyxel, Multiple Firewalls. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-78 OS Command Injection — weakness family: Injection.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft malicious packets targeting the error handling mechanism of exposed Zyxel firewalls.
Business
Perimeter security is compromised without authentication requirements or user interaction.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I inject OS commands through the error message processing to achieve remote code execution.
Business
Attackers gain full system-level access to critical network infrastructure.
3
Lateral reach — past segmentation narrative 3
Attacker
I establish persistence and pivot deeper into the network from the compromised firewall.
Business
Internal systems and data become accessible to threat actors operating from trusted perimeter devices.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05