CVE-2023-28771: Zyxel ZyWALL/USG series firmware · OS Command Injection
Affects Zyxel ZyWALL/USG series firmwareSource CVE Database V5
Exploited in the wild · KEV due 21 Jun 2023 · public exploit available (Metasploit) · 99% EPSS : apply the vendor's fix or mitigations to Zyxel ZyWALL/USG series firmware now.
Data as of 25 Oct 2026, 19:02 UTC
- KEV deadline
- US federal agencies must patch by this date; a sensible deadline for everyone else.
- EPSS
- 99.2% chance of exploitation in 30 days – higher than 99% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
t = 0 is the CVE’s publication on cve.org
Disclosed: evidence found.
CVE published 25 Apr 2023
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: evidence found.
Exploited in the wildExploited: evidence found.
Listed in CISA KEV 36 days after disclosure
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
Timeline
CVE ID reserved
by Zyxel
, 33 days before disclosure
CVE published
on cve.org
, t = 0
Added to CISA KEV (opens in a new tab)
exploitation confirmed
, 36 days after disclosure
KEV remediation due
US federal deadline
, 57 days after disclosure
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA KEV (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Zyxel ZyWALL/USG series firmware | Affected
| Fixed in– |
Check the firmware or software version for Zyxel ZyWALL/USG series firmware in the device's admin interface against the vendor advisory.
Description
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.
References
- zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-remote-command-injection-vulnerability-of-firewalls (opens in a new tab)
- packetstormsecurity.com/files/172820/Zyxel-IKE-Packet-Decoder-Unauthenticated-Remote-Code-Execution.html (opens in a new tab)
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-28771 (opens in a new tab)