CVE-2023-28771

Exp

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.

Published: 2023-04-25 Last update: 2025-10-27 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-28771 is rated Critical Active Threat (100/100): CVSS Critical severity, with high exploitation likelihood (EPSS 99.28%, 100th percentile). CISA KEV confirms active exploitation (added 2023-05-31) affecting Zyxel / Multiple Firewalls. a weakness (CWE-78) Unauthenticated remote administrative access may be possible. EPSS rose +4.94% over the last day, indicating growing attacker interest. The CISA remediation deadline has passed—treat as an emergency patch priority.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

CISA KEV Record for CVE-2023-28771

Name: Zyxel Multiple Firewalls OS Command Injection Vulnerability · CISA KEV detail

Exploit added: 2023-05-31

Action due: 2023-06-21

Required action: Apply updates per vendor instructions.

Public exploit references (Exploit-DB) for CVE-2023-28771

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2023-28771

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 94.35% 99.28% +4.94%
2 2025-12-18 94.35% 94.35% -0.01%
3 2025-11-21 — 94.35% —

Full EPSS history (35 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-28771

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]

Weakness enumeration for CVE-2023-28771

Affected software / configurations for CVE-2023-28771

Vendor Product Version Raw CPE
zyxel atp100_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:atp100_firmware:*:*:*:*:*:*:*:*
zyxel atp100w_firmware >= 4.60, < 5.35 cpe:2.3:o:zyxel:atp100w_firmware:*:*:*:*:*:*:*:*
zyxel atp200_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:atp200_firmware:*:*:*:*:*:*:*:*
zyxel atp500_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:atp500_firmware:*:*:*:*:*:*:*:*
zyxel atp700_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:atp700_firmware:*:*:*:*:*:*:*:*
zyxel atp800_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:atp800_firmware:*:*:*:*:*:*:*:*
zyxel usg_flex_100_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:usg_flex_100_firmware:*:*:*:*:*:*:*:*
zyxel usg_flex_100w_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:usg_flex_100w_firmware:*:*:*:*:*:*:*:*
zyxel usg_flex_200_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:usg_flex_200_firmware:*:*:*:*:*:*:*:*
zyxel usg_flex_50_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:usg_flex_50_firmware:*:*:*:*:*:*:*:*
zyxel usg_flex_500_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:usg_flex_500_firmware:*:*:*:*:*:*:*:*
zyxel usg_flex_50w_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:usg_flex_50w_firmware:*:*:*:*:*:*:*:*
zyxel usg_flex_700_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:usg_flex_700_firmware:*:*:*:*:*:*:*:*
zyxel vpn100_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:vpn100_firmware:*:*:*:*:*:*:*:*
zyxel vpn1000_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:vpn1000_firmware:*:*:*:*:*:*:*:*
zyxel vpn300_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:vpn300_firmware:*:*:*:*:*:*:*:*
zyxel vpn50_firmware >= 4.60, < 5.36 cpe:2.3:o:zyxel:vpn50_firmware:*:*:*:*:*:*:*:*
zyxel zywall_usg_310_firmware >= 4.60, < 4.73 cpe:2.3:o:zyxel:zywall_usg_310_firmware:*:*:*:*:*:*:*:*
zyxel zywall_usg_310_firmware 4.73 cpe:2.3:o:zyxel:zywall_usg_310_firmware:4.73:-:*:*:*:*:*:*
zyxel zywall_usg_100_firmware >= 4.60, < 4.73 cpe:2.3:o:zyxel:zywall_usg_100_firmware:*:*:*:*:*:*:*:*
zyxel zywall_usg_100_firmware 4.73 cpe:2.3:o:zyxel:zywall_usg_100_firmware:4.73:-:*:*:*:*:*:*

References for CVE-2023-28771

cvelogic Threat Intelligence