NVD / CVE Program· CNA Zyxel

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.

Noroxi assessment

Priority: Now (action score 99/100)

CISA has confirmed exploitation in the wild (May 31, 2023). Remediation deadline for US federal agencies: Jun 21, 2023.
A ready-made attack module is public (Metasploit, Nuclei); exploiting it takes no special expertise.
Probability of exploitation in the next 30 days: 99.2% (FIRST EPSS); higher than 99.9% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
According to the record, no fixed version is available yet.
Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Patch today or shut off access. Until a fix is released, restrict access to the affected component and follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · CISA KEV · FIRST EPSS

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.

CriticalCVSS 9.8 · v3.1KEVWeaponized No fix recorded

BDU:2023-02782

Published: Apr 24, 2023
Updated: Jun 17, 2026
EPSS: 99.2% · 99th percentile
CWE: CWE-78

Report tools

JSON

Action score

Now

Patch today or shut off access.

CVSS: 39 / 40 · 9.8 / 10
CISA KEV: 30 / 30 · Listed
EPSS: 30 / 30 · 99.2%

CISA SSVC decision

Exploitation: active
Automatable: yes
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · Zyxel: 9.8; NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Actively exploited in the wild

CISA added this to its Known Exploited Vulnerabilities catalog on May 31, 2023. That signals real attacks, not theory.

Remediation deadline for US federal agencies: Jun 21, 2023.

Get told when this record changes

In CISA KEV: exploitation in the wild confirmed
Weaponized exploit exists
No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
zyxel	atp100 firmware	cpe:2.3:o:zyxel:atp100_firmware
zyxel	atp100	cpe:2.3:h:zyxel:atp100
zyxel	atp100w firmware	cpe:2.3:o:zyxel:atp100w_firmware
zyxel	atp100w	cpe:2.3:h:zyxel:atp100w
zyxel	atp200 firmware	cpe:2.3:o:zyxel:atp200_firmware
zyxel	atp200	cpe:2.3:h:zyxel:atp200
zyxel	atp500 firmware	cpe:2.3:o:zyxel:atp500_firmware
zyxel	atp500	cpe:2.3:h:zyxel:atp500
zyxel	atp700 firmware	cpe:2.3:o:zyxel:atp700_firmware
zyxel	atp700	cpe:2.3:h:zyxel:atp700
zyxel	atp800 firmware	cpe:2.3:o:zyxel:atp800_firmware
zyxel	atp800	cpe:2.3:h:zyxel:atp800

and 26 more

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

zyxel atp100 firmware4.60 and later · before 5.36
zyxel atp100w firmware4.60 and later · before 5.35
zyxel atp200 firmware4.60 and later · before 5.36
zyxel atp500 firmware4.60 and later · before 5.36
zyxel atp700 firmware4.60 and later · before 5.36
zyxel atp800 firmware4.60 and later · before 5.36
zyxel usg flex 100 firmware4.60 and later · before 5.36
zyxel usg flex 100w firmware4.60 and later · before 5.36
zyxel usg flex 200 firmware4.60 and later · before 5.36
zyxel usg flex 50 firmware4.60 and later · before 5.36
zyxel usg flex 500 firmware4.60 and later · before 5.36
zyxel usg flex 50w firmware4.60 and later · before 5.36
zyxel usg flex 700 firmware4.60 and later · before 5.36
zyxel vpn100 firmware4.60 and later · before 5.36
zyxel vpn1000 firmware4.60 and later · before 5.36
zyxel vpn300 firmware4.60 and later · before 5.36
zyxel vpn50 firmware4.60 and later · before 5.36
zyxel zywall usg 100 firmware4.60 and later · before 4.73
zyxel zywall usg 100 firmware4.73
zyxel zywall usg 310 firmware4.60 and later · before 4.73

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Zyxel). Independent of NVD's CPE analysis and usually ahead of it.

Zyxel ATP series firmware
- 4.60 through 5.35affected
Zyxel USG FLEX series firmware
- 4.60 through 5.35affected
Zyxel VPN series firmware
- 4.60 through 5.35affected
Zyxel ZyWALL/USG series firmware
- 4.60 through 4.73affected

Same product

zyxel: all records

Other highest-scoring records for the same primary product.

CVE-2023-33010A buffer overflow vulnerability in the ID processing function in Zyxel ATP series firmware versions 4.32 through 5.36 Patch 1, USG FLEX seriKEV
78This week
CVE-2023-33009A buffer overflow vulnerability in the notification function in Zyxel ATP series firmware versions 4.60 through 5.36 Patch 1, USG FLEX serieKEV
77This week
CVE-2023-6764 A format string vulnerability in a function of the IPSec VPN feature in Zyxel ATP series firmware versions from 4.32 through 5.3
32Monitor

Published before and after this one in the same product

← EarlierCVE-2022-38547Feb 6, 2023 · A post-authentication command injection vulnerability in the CLI command of Zyxel ZyWALL/USG series firmware versions 4.20 through 4.72, VPN
29Monitor
Later →CVE-2023-6397Feb 19, 2024 · A null pointer dereference vulnerability in Zyxel ATP series firmware versions from 4.32 through 5.37 Patch 1 and USG FLEX serie
21Monitor
Later →CVE-2023-6398Feb 19, 2024 · A post-authentication command injection vulnerability in the file upload binary in Zyxel ATP series firmware versions from 4.32 through 5.37
28Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

Weaponized

A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.

Evidence

Metasploit module ×1
Nuclei detection template ×1
Proof-of-concept repository on GitHub ×2

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
Source	Kind	Date
Metasploit module	exploit/linux/misc/zyxel_ike_decoder_rce_cve_2023_28771Zyxel IKE Packet Decoder Unauthenticated Remote Code Executionexploit	2023-03-31
Nuclei detection template	Nuclei template unauth-ztp-ping	—
Proof-of-concept repository on GitHub	stars:30	2023-05-23
Proof-of-concept repository on GitHub	stars:0	2025-07-22

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

MetasploitMar 31, 2023-25 d
PublishedApr 24, 2023
First PoCMay 23, 2023+28 d
CISA KEVMay 31, 2023+36 d
TodayNov 6, 2026+1291 d

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

TR-23-0240 · Apr 25, 2023(Zyxel Güvenlik Bildirimi)

All national notices →

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: high · data can be read
Integrity: high · data or configuration can be modified
Availability: high · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: High

Weakness class (CWE)

CWE-78 · Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-secondary

Root cause

User input is inserted as text into a shell command. The shell may interpret special characters in the input as part of the command.

The bug in code

The whole CWE-78 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1const host = req.body.host;
2exec("ping -c 1 " + host, onResult);

Fixed

1const host = req.body.host;
2if (!/^[a-z0-9.-]{1,253}$/i.test(host)) return res.sendStatus(400);
3execFile("ping", ["-c", "1", host], onResult);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

—

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-remote-command-injection-vulnerability-of-firewalls

Show all references (1 more)

www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-28771

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records

Noroxi analysis

What does it mean in your environment?

We use this product, ask for help

Data sources and verification

CNA: Zyxel

CVE.org (CNA)Oct 21, 2025, 11:05 PM UTC
CISA ADPOct 21, 2025, 11:05 PM UTC
NVDJun 17, 2026, 1:48 AM UTC
FIRST EPSSOct 25, 2026, 12:00 AM UTC
MetasploitNov 5, 2026, 3:17 AM UTC
NucleiNov 5, 2026, 3:17 AM UTC
PoC-in-GitHubNov 5, 2026, 3:18 AM UTC

Each line is when that source was last processed for this record.