No exploitation reportedFix available

CVE-2018-4850

Q: Is CVE-2018-4850 actively exploited?

Active exploitation of CVE-2018-4850 has not been confirmed. Its EPSS score was 2.4% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2018-4850?

CVE-2018-4850 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

No exploitation reported by the sources we read.

Published2018-05-16
Fixed in5.2
WeaknessCWE-20

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC

2018-05-1617:29CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2018-4850?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2018-4850?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Siemens simatic s7-400 firmwareversion to verify

Branch	Affected	Fixed in	Source
5.2	< 5.2	5.2	NVD
4.0	≤ 4.0	no fix published	NVD

Siemens simatic s7-400h firmwareversion to verify

Branch	Affected	Fixed in	Source
4.5	≤ 4.5	no fix published	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

ICSA-18-137-03 CISA3 known affected
Siemens SIMATIC S7-400 CPU (Update A)
Siemens SIMATIC S7-400 CPU hardware version 4.0 and below (incl. SIPLUS variants): All versions · Siemens SIMATIC S7-400 CPU hardware version 5.0 (incl. SIPLUS variants): All firmware versions < V5.2 · Siemens SIMATIC S7-400 H CPU hardware version 4.5 and below (incl. SIPLUS variants): All versions

Full record on NVD

Fix

Update Siemens simatic s7-400 firmware to 5.2
Vendor fix CISA ICSA-18-137-03 · 1 productUpdate to firmware version 5.2 or newer https://support.industry.siemens.com/cs/ww/en/view/109474827
Vendor fix CISA ICSA-18-137-03 · 1 productUpgrade to hardware version 5.0 or newer https://support.industry.siemens.com/cs/ww/en/view/109483507
Vendor fix CISA ICSA-18-137-03 · 1 productUpgrade to hardware version 6.0 or newer https://support.industry.siemens.com/cs/ww/en/view/109483507
Mitigation from the vendor CISA ICSA-18-137-03 · 3 productsApply cell protection concept: https://www.siemens.com/cert/operational-guidelines-industrial-security.
Mitigation from the vendor CISA ICSA-18-137-03 · 3 productsUse VPN for protecting network communication between cells.
Mitigation from the vendor CISA ICSA-18-137-03 · 3 productsApply Defense-in-Depth: https://www.siemens.com/cert/operational-guidelines-industrial-security.

Advisories and patches

cert-portal.siemens.comVendor Advisory
www.siemens.comVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.07.5read 2026-10-23
NVDCVSS 2.05read 2026-10-23
CNAweakness (CWE)CWE-20read 2026-10-23
FIRST EPSSEPSS score2.4 %2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published: 2018-05-16
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2018-4850?

Is CVE-2018-4850 actively exploited?

Active exploitation of CVE-2018-4850 has not been confirmed. Its EPSS score was 2.4% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2018-4850?

CVE-2018-4850 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Running SIMATIC S7-400 (incl? Hear about its next vulnerability

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