Exploitation evidence
Known exploited · CISA KEV listed
Added 2023-05-31. Ransomware campaign use: Unknown.
CISA required action: Apply updates per vendor instructions.
CISA due date: 2023-06-21. This is the catalog’s deadline, not an assessment of your organization’s exposure.
KEV checked 13 Nov 2026, 00:20 Jerusalem · Original catalog ↗Reported products and versions
Zyxel / ZyWALL/USG series firmware
Default status: Not specified
- affected: 4.60 through 4.73
Zyxel / VPN series firmware
Default status: Not specified
- affected: 4.60 through 5.35
Zyxel / USG FLEX series firmware
Default status: Not specified
- affected: 4.60 through 5.35
Zyxel / ATP series firmware
Default status: Not specified
- affected: 4.60 through 5.35
Fixes and workarounds
No explicit solution text in the downloaded CVE record. Consult the vendor advisory; unaffected version ranges are shown above as reported, not inferred as a patch recommendation.
Sources and related reporting
CVE Program record ↗ · Download tracked evidence as JSON
- https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-remote-command-injection-vulnerability-of-firewalls
- http://packetstormsecurity.com/files/172820/Zyxel-IKE-Packet-Decoder-Unauthenticated-Remote-Code-Execution.html
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-28771
Observed change timeline
History begins when Egret first downloads each source. It is not the complete upstream CVE history.
12 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-12",
"epss": 0.99284,
"percentile": 0.99938
}10 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-10",
"epss": 0.99284,
"percentile": 0.99937
}09 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-09",
"epss": 0.99284,
"percentile": 0.99937
}08 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-08",
"epss": 0.99284,
"percentile": 0.99937
}07 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-07",
"epss": 0.99284,
"percentile": 0.99937
}06 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-06",
"epss": 0.99284,
"percentile": 0.99937
}06 Nov 2026, 06:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-05",
"epss": 0.99284,
"percentile": 0.99937
}04 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-04",
"epss": 0.99284,
"percentile": 0.99937
}04 Nov 2026, 18:20 Jerusalem · CVE Program record changed
Stored CNA snapshot at this observation.
{
"containers": {
"adp": [
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"dateUpdated": "2024-08-02T13:51:38.311Z",
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{
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"url": "http://packetstormsecurity.com/files/172820/Zyxel-IKE-Packet-Decoder-Unauthenticated-Remote-Code-Execution.html"
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"title": "CVE Program Container"
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{
"metrics": [
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"version": "2.0.3"
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"cna": {
"affected": [
{
"product": "ZyWALL/USG series firmware",
"vendor": "Zyxel",
"versions": [
{
"status": "affected",
"version": "4.60 through 4.73"
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{
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{
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{
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"metrics": [
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"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
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{
"url": "http://packetstormsecurity.com/files/172820/Zyxel-IKE-Packet-Decoder-Unauthenticated-Remote-Code-Execution.html"
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"datePublished": "2023-04-25T00:00:00.000Z",
"dateReserved": "2023-03-23T00:00:00.000Z",
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"state": "PUBLISHED"
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}03 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-03",
"epss": 0.99284,
"percentile": 0.99937
}03 Nov 2026, 02:22 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-02",
"epss": 0.99284,
"percentile": 0.99937
}03 Nov 2026, 02:22 Jerusalem · CISA KEV status changed
Stored KEV snapshot at this observation.
{
"cveID": "CVE-2023-28771",
"cwes": [
"CWE-78"
],
"dateAdded": "2023-05-31",
"dueDate": "2023-06-21",
"forensicTriage": "No",
"knownRansomwareCampaignUse": "Unknown",
"notes": "https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-remote-command-injection-vulnerability-of-firewalls; https://nvd.nist.gov/vuln/detail/CVE-2023-28771",
"product": "Multiple Firewalls",
"requiredAction": "Apply updates per vendor instructions.",
"shortDescription": "Zyxel ATP, USG FLEX, VPN, and ZyWALL/USG firewalls allow for improper error message handling which could allow an unauthenticated attacker to execute OS commands remotely by sending crafted packets to an affected device.",
"vendorProject": "Zyxel",
"vulnerabilityName": "Zyxel Multiple Firewalls OS Command Injection Vulnerability"
}