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CVE-2023-28771VulnerabilityPublished Updated

CVE-2023-28771: Zyxel ZyWALL/USG series firmware · OS Command Injection

Affects Zyxel ZyWALL/USG series firmwareSource CVE Database V5

0

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

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
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:H

Exploitation evidence

t = 0 is the CVE’s publication on cve.org

  1. Disclosed: evidence found.

    CVE published 25 Apr 2023

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: evidence found.

    1 Metasploit module

  4. Exploited in the wild: evidence found.

    Listed in CISA KEV 36 days after disclosure

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

Timeline

  1. CVE ID reserved

    by Zyxel

    , 33 days before disclosure

  2. CVE published

    on cve.org

    , t = 0

  3. , 36 days after disclosure

  4. 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

ProductAffectedFixed in
Zyxel ZyWALL/USG series firmwareAffected
  • >=4.60 <=4.73
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

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