A vulnerability has been identified in SIMATIC S7-400 (incl.

published 2018-05-16 8 y ago modified 2026-06-17 4 mo ago also EUVD-2018-16636

cvss: 7.5; version 3.0, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 2.4%; EPSS 2.4% chance of exploitation in 30 days, percentile 83%
public exploits: 0; none known

A vulnerability has been identified in SIMATIC S7-400 (incl. F) CPU hardware version 4.0 and below (All versions), SIMATIC S7-400 (incl. F) CPU hardware version 5.0 (All firmware versions < V5.2), SIMATIC S7-400H CPU hardware version 4.5 and below (All versions). The affected CPUs improperly validate S7 communication packets which could cause a Denial-of-Service condition of the CPU. The CPU will remain in DEFECT mode until manual restart.

Patch / fix

fixed in 1

siemens simatic_s7-400_firmware 5.2

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

cisa ICSA-18-137-03 updated 2020-02-10 cvss 7.5

Siemens SIMATIC S7-400 CPU (Update A)

Siemens SIMATIC S7-400 CPU hardware version 4.0 and below (incl. SIPLUS variants) Siemens SIMATIC S7-400 CPU hardware version 5.0 (incl. SIPLUS variants) <firmware_V5.2 Siemens SIMATIC S7-400 H CPU hardware version 4.5 and below (incl. SIPLUS variants)
affected: vendor fix, mitigation

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

Exploit prediction

2.38% chance of exploitation in the next 30 days, higher than 83% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
NVD	3.0	7.5	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:N/A:P

Affected products

Siemens AG SIMATIC S7-400 (incl. F) CPU hardware version 4.0 and below, SIMATIC S7-400 (incl. F) CPU hardware version 5.0, SIMATIC S7-400H CPU hardware version 4.5 and below

Classification

Weakness

CWE-20 Improper Input Validation

References

cert-portal.siemens.com /productcert/pdf/ssa-914382.pdf
vendor-advisory
siemens.com /global/en/home/products/services/cert.html#SecurityPublications
vendor-advisory
securityfocus.com /bid/104217
vdb-entry, third-party-advisory

Sources

CVE List CVE-2018-4850
NVD CVE-2018-4850

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary