What is CVE-2023-28771?

CVE-2023-28771 is a critical-severity vulnerability in Zyxel Atp100, classified under OS Command Injection. CVSS score: 9.8/10. Published 2023-04-25.

How severe is CVE-2023-28771?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2023-28771 known to be exploited?

Yes. CVE-2023-28771 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2023-05-31), indicating it is being actively exploited. 16 public proof-of-concept repositories are indexed.

RCE in Zyxel Atp100

CVE-2023-28771

Improper error message handling in Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware versions 4.60 through 5.35, USG FLEX series firmware versions 4.60 through 5.35, and ATP series firmware versions 4.60 through 5.35, which could allow an unauthenticated attacker to execute some OS commands remotely by sending crafted packets to an affected device.

Vulnerability class: Command Injection (OS Command Injection)

Published 2023-04-25 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.993 (99.9th percentile), scored 2026-10-15.

Very high probability of exploitation in the next 30 days — among the top 0.1% most-likely-to-be-exploited CVEs. 100th percentile — 99.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.993 · newest: 0.993 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-78 — OS Command Injection

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2023-05-31. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2023-06-21.

Required action: Apply updates per vendor instructions.

Public proof-of-concept exploits

References

www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for… (Vendor Advisory)
packetstormsecurity.com/files/172820/Zyxel-IKE-Packet-Decoder-Unauthenticated-R… (Exploit, Third Party Advisory)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)

Frequently asked questions

What is CVE-2023-28771?: CVE-2023-28771 is a critical-severity vulnerability in Zyxel Atp100, classified under OS Command Injection. CVSS score: 9.8/10. Published 2023-04-25.
How severe is CVE-2023-28771?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2023-28771 known to be exploited?: Yes. CVE-2023-28771 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2023-05-31), indicating it is being actively exploited. 16 public proof-of-concept repositories are indexed.