vciy

CVE-2023-28771

INDEX BUILT · 2026-09-20

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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…

CVE-2023-287714 of 4 sources documented this
81

rank 81 = 40 + 25 + 0 + 10 + 6

rank@v1 · act now

Someone is already using it

CISA KEV catalog · public proof-of-concept · FIRST EPSS

EPSS 0.99284 · CISA KEV listed  ·  without this subject the record ranks 41

What it costs you if it fires

NVD CVSS base score, then the CNA's own

CVSS 9.8, from the CNA  ·  without this subject the record ranks 56

It is getting worse, not staying still

FIRST EPSS series, rescorings and bad loads removed

no persisting rise in 365 days  ·  without this subject the record ranks 81

How much of the world it touches

NVD CPE configurations

20 products in the CPE ranges  ·  without this subject the record ranks 71

Someone else already set the date

CISA KEV remediation due date

CISA remediation date held  ·  without this subject the record ranks 75

Unaudited dollar value2 of 3 inputs carry a receipt
Exposure$4.95Mover the next 30 days, if this record is yours
Movement+$230,000on 2025-11-21, the last material move, 9 months before this reading
Basisassumeda published average, not your estate

$4.95M = $4.99M incident cost x 1 exposure x 0.99284 likelihood

udv@v1 · unaudited · wrong for you until you say what you run

$4.99M is the cost of a breach that happened, from IBM Cost of a Data Breach Report 2026, global average. It is not the value of any asset of yours. That average already covers breaches of every severity, so scaling it by exposure understates a partial-impact record. That is an assumption, not a measurement. Your own asset value goes in the decision record.

Hindsight · the state

0.99284EPSSKEV · LISTED
Severity9.8 CRITICALreceipt
Harmtotal loss · unauthenticatedreceipt
Exploitationin the wild · KEVreceipt
Defenseunaffected versions publishedreceipt
Movementscoring model changedreceipt
PLATEAU10Minimal movement since 2025-03-17, 536 days at 0.99, as of 2026-09-04. arc-rules@v1

Foresight · where to check next

CVE-2023-43208CVE-2021-27104CVE-2019-15107CVE-2019-16057CVE-2018-10562CVE-2018-1113828771

This record is one instance of CWE-78, improper neutralization of special elements used in an os command ('os command injection'). The index holds 6775 prior instances of this class, 121 KEV-listed. The nearest of its KEV-listed records are drawn beside this. taxonomy@v1

Full pattern panel

Prior records in this weakness class. Each is its own record, dated and receipted.
Color is a claim, not decoration:the hostile worldthe defenseno signalspoke length is how much of the record matches, not how bad it is

Running Zyxel ZyWALL/USG series firmware? Check your version

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Reachnetwork-reachable · no privileges required · no user interaction · low attack complexityreceipt
ImpactComplete confidentiality, integrity and availability lossreceipt
Scored fromCVSS v3.1 · the CNA's vectorreceipt
Weakness classCWE-78 Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')receipt
Published consequencesCWE-78: Confidentiality, Integrity, Availability, Non-Repudiation: Execute Unauthorized Code or Commands, DoS: Crash, Exit, or Restart, Read Files or Directories, Modify Files or Directories, Read…[email protected]
Ransomware campaign useUnknown to CISAreceipt

CISA KEV & Federal Remediation Deadline from the record and CISA

The fix, and how long it's been waiting.

First unaffected version, by branchusg flex 5.36; zywall usg 4.73; atp100 firmware 5.36; atp100w firmware 5.35; atp200 firmware 5.36; atp500 firmware 5.36receipt
Patch available sinceNo dated patch-availability record in held sources. The index holds reference URLs without dates and only the current revision of the CVE record, so the day a fix first existed cannot be derived. Only the versions it landed in.
CISA remediation statusoverdue since 2023-06-21receipt
CISA required actionApply updates per vendor instructions.receipt
Published to CISA KEV36 daysderived

Exploit Status & Known PoCs a ladder, not a score

Current rung: Exploited in the wild · CISA KEV listed, 2023-05-31.

  • RUNG 1Nothing observed in held sources
  • RUNG 2Proof-of-concept published · 2 public repositories2023-05-23receipt
  • RUNG 3Exploited in the wild · CISA KEV listed2023-05-31receipt
  • RUNG 4Ransomware campaign use known

Authority who says so

CVSS, the CNA9.8 CRITICALreceipt
Exploit probability0.99284 · top 0.06% of all CVEsreceipt
Blast breadth14 products across 1 vendorderived
Assigned byZyxelreceipt
Recorded changes55 · last 19 Sep 2026derived

Affected & Fixed Versions as published

Affected productZyxel ZyWALL/USG series firmware; Zyxel VPN series firmware; Zyxel USG FLEX series firmware; Zyxel ATP series firmwarereceipt
Published rangeszyxel atp100 firmware >= 4.60 < 5.36; zyxel atp100w firmware >= 4.60 < 5.35; zyxel atp200 firmware >= 4.60 < 5.36; zyxel atp500 firmware >= 4.60 < 5.36receipt
Show all 20 published ranges
zyxel atp100 firmware >= 4.60 < 5.36
zyxel atp100w firmware >= 4.60 < 5.35
zyxel atp200 firmware >= 4.60 < 5.36
zyxel atp500 firmware >= 4.60 < 5.36
zyxel atp700 firmware >= 4.60 < 5.36
zyxel atp800 firmware >= 4.60 < 5.36
zyxel usg flex 100 firmware >= 4.60 < 5.36
zyxel usg flex 100w firmware >= 4.60 < 5.36
zyxel usg flex 200 firmware >= 4.60 < 5.36
zyxel usg flex 50 firmware >= 4.60 < 5.36
zyxel usg flex 500 firmware >= 4.60 < 5.36
zyxel usg flex 50w firmware >= 4.60 < 5.36
zyxel usg flex 700 firmware >= 4.60 < 5.36
zyxel vpn100 firmware >= 4.60 < 5.36
zyxel vpn1000 firmware >= 4.60 < 5.36
zyxel vpn300 firmware >= 4.60 < 5.36
zyxel vpn50 firmware >= 4.60 < 5.36
zyxel zywall usg 310 firmware >= 4.60 < 4.73
zyxel zywall usg 310 firmware 4.73
zyxel zywall usg 100 firmware >= 4.60 < 4.73

A rung lights from a row in the index, never from an assessment. "Held sources" is the true scope of the claim: this index reads the CVE record, NVD, CISA KEV, FIRST's EPSS and public proof-of-concept repositories, and it does not observe attacks.

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Attack path

Unauthenticated network requestno credentials, no interactionCISA KEV listingadded 05-31 · due 06-21Zyxel VPN series firmwareCWE-78 OS command injectionFull compromise (C/I/A)C:H / I:H / A:Hmandates remediationexploits CWE-78data compromise

What it is stated by the CNA

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. receipt

NVD's analysis a second authority

weakness
CWE-78
affected versions
zyxel atp100 firmware >= 4.60 < 5.36; zyxel atp100w firmware >= 4.60 < 5.35; zyxel atp200 firmware >= 4.60 < 5.36; and 17 more, listed in full below
also scored by
[email protected] 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H · [email protected] 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

check it yourself zyxel.com packetstormsecurity.com receipt

Dated events

2023-05-31Added to CISA KEV2023-06-01EPSS moved 0.00 to 0.202023-06-21CISA remediation due2024-12-17EPSS moved 0.88 to 0.082025-11-21EPSS moved 0.90 to 0.94

Movement the material steps

25 Apr 20230.00045
1 Jun 20230.19673 · crossed 0.10
10 Jun 20230.91122 · crossed 0.50 and 0.90
8 Jul 20230.89947 · crossed 0.90
27 Jul 20230.91881 · crossed 0.90
30 Jul 20240.89408 · crossed 0.90
17 Dec 20240.07798 · crossed 0.10 and 0.50
14 Mar 20250.82469 · crossed 0.10 and 0.50
17 Mar 20250.90622 · crossed 0.90 · scoring model v2025.03.14
18 Nov 20250.89749 · crossed 0.90
21 Nov 20250.94354 · crossed 0.90
15 Jun 20260.99284 · scoring model v2026.06.15

This score more than doubled inside 72 hours. Both observations are in the full history below.

Show all 41 observations
25 Apr 20230.00045
5 May 20230.00100
8 May 20230.00158
23 May 20230.00229
1 Jun 20230.19673
10 Jun 20230.91122
26 Jun 20230.91789
29 Jun 20230.90560
8 Jul 20230.89947
27 Jul 20230.91881
27 Aug 20230.91711
11 Sep 20230.92655
30 Oct 20230.93051
7 Nov 20230.91855
11 Dec 20230.92380
14 Mar 20240.92234
25 Mar 20240.91766
6 Apr 20240.92162
1 May 20240.91403
27 May 20240.91864
4 Jul 20240.90214
30 Jul 20240.89408
26 Aug 20240.89828
8 Sep 20240.89646
22 Sep 20240.88355
5 Oct 20240.86228
18 Oct 20240.87746
15 Nov 20240.87671
17 Dec 20240.07798
11 Feb 20250.06866
11 Mar 20250.06927
14 Mar 20250.82469
17 Mar 20250.90622
15 Apr 20250.9435
22 Oct 20250.94354
18 Nov 20250.89749
21 Nov 20250.94354
18 Dec 20250.94346
2 May 20260.94305
2 Jun 20260.94346
15 Jun 20260.99284

41 observations held. A highlighted step crossed a promotion threshold. A step marked with a scoring model moved because the instrument was replaced, not because the vulnerability changed. receipt

The full biography

EPSS 0.99284Published2023-04-25Public PoC2023-05-23CISA KEV2023-05-31Index as of2026-09-04

Listed by CISA 36 days after it published, exploit probability more than doubled between 2025-03-11 and 2025-03-14 (0.06927 → 0.82469) and the record had been public for 3 years, 4 months when this index was last written.

No material movement in 81 days as of the last ingest this index recorded.

Published 2023-04-25 receipt · Public PoC 2023-05-23 receipt · CISA KEV 2023-05-31 receipt · Index as of 2026-09-04 derived

The pattern, elsewhere

This record is one instance of CWE-78, improper neutralization of special elements used in an os command ('os command injection'). The index holds 6775 prior instances of this class, 121 KEV-listed. The nearest of its KEV-listed records are drawn beside this. [email protected]

CVE-2023-43208matches 8 of 8KEV listed · 2023receipt
CVE-2021-27104matches 8 of 8KEV listed · 2021receipt
CVE-2019-15107matches 8 of 8KEV listed · 2019receipt
CVE-2019-16057matches 8 of 8KEV listed · 2019receipt
CVE-2018-10562matches 8 of 8KEV listed · 2018receipt
CVE-2018-11138matches 8 of 8KEV listed · 2018receipt

"Matches n of m" counts the attributes the two records can both be compared on: the CVSS metrics they share a version of, any weakness class beyond this one, and the vendor. fit-rules@v1

6775 records in this class held. The six above are drawn from the ones CISA has listed as exploited, ranked by how much of the record matches this one. That is why every one of them is KEV-listed: the pool is, so the colour on those spokes says nothing the pool has not already said.

No curated product neighbourhood is held for this product, so the records above are the nearest this index can name. The neighbourhood table covers a small set of products and is extended by hand.

Siblings and hubs

Records related to this one

Its defect family

zyxel zywall/usg series firmware

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Family membership: held values

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