CVE-2023-28771
CriticalExploitedPublic exploitImproper 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…
Published Apr 25, 2023 · Updated Oct 21, 2025
Key Facts
Patch immediately- CVE-2023-28771 is a critical-severity vulnerability (CVSS 9.8 v3.1) affecting Atp100 Firmware (Zyxel), Atp100w Firmware (Zyxel), Atp200 Firmware (Zyxel) and 20 more products.
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since May 25, 2023. Public exploit code is available.
- EPSS estimates a 99% probability of exploitation in the next 30 days.
- Fixed versions are available, including Atp100 Firmware 5.36, Atp100w Firmware 5.35, Atp200 Firmware 5.36.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
9.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
99%
Higher than 99.9% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2023-28771 brief as a PDF
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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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | May 31, 2023 | Jun 21, 2023 | Not reported |
| Industry KEV feed | May 25, 2023 | Jun 21, 2023 | Not reported |
| CIRCL KEV | May 31, 2023 | Jun 21, 2023 | Not reported |
| ENISA EUVD | May 31, 2023 | n/a | Not reported |
Required action: Apply updates per vendor instructions.
Affected Products
25 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Atp100 FirmwareZyxel | See advisory | 5.36 |
| Atp100w FirmwareZyxel | See advisory | 5.35 |
| Atp200 FirmwareZyxel | See advisory | 5.36 |
| Atp500 FirmwareZyxel | See advisory | 5.36 |
| Atp700 FirmwareZyxel | See advisory | 5.36 |
Patched Releases
Atp100 Firmware
5.36
Atp100w Firmware
5.35
Atp200 Firmware
5.36
Atp500 Firmware
5.36
Atp700 Firmware
5.36
Atp800 Firmware
5.36
Usg Flex 100 Firmware
5.36
Usg Flex 100w Firmware
5.36
Usg Flex 200 Firmware
5.36
Usg Flex 50 Firmware
5.36
Usg Flex 500 Firmware
5.36
Usg Flex 50w Firmware
5.36
Usg Flex 700 Firmware
5.36
Vpn100 Firmware
5.36
Vpn1000 Firmware
5.36
Vpn300 Firmware
5.36
Vpn50 Firmware
5.36
Zywall Usg 100 Firmware
4.73
Zywall Usg 310 Firmware
4.73
Timeline
Publicly disclosed
Apr 25, 2023
Added to Industry KEV feed
May 25, 2023
Added to CISA KEV
May 31, 2023
Added to CIRCL KEV
May 31, 2023
Added to ENISA EUVD
May 31, 2023
Last updated
Oct 21, 2025
Weakness Type
- CWE-78 Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
References
- advisoryhttps://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2023-22913
- advisoryhttps://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2023-22914
- advisoryhttps://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2023-22915
- advisoryUSOM advisory
- advisoryhttps://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-vulnerabilities-of-firewalls-and-aps
FAQ
Common Questions.
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 comma…
Affected: Atp100 Firmware (Zyxel); Atp100w Firmware (Zyxel); Atp200 Firmware (Zyxel), among others. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since May 25, 2023.
Yes. It was added on May 31, 2023 with a federal remediation due date of Jun 21, 2023.
Public exploit code is available.
Fixed versions are available, including Atp100 Firmware 5.36, Atp100w Firmware 5.35, Atp200 Firmware 5.36.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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