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Simatic S7 300 Cpu 312 FirmwareOperating system · Siemens

CVE-2020-15791

MEDIUM · 6.5 CVSS v3.1 Published 2020-09-09
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
70/100
Remediation priority · Elevated
No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A vulnerability has been identified in SIMATIC S7-300 CPU family (incl. related ET200 CPUs and SIPLUS variants) (All versions), SIMATIC S7-400 CPU family (incl. SIPLUS variants) (All versions), SIMATIC WinAC RTX (F) 2010 (All versions), SINUMERIK 840D sl (All versions). The authentication protocol between a client and a PLC via port 102/tcp (ISO-TSAP) insufficiently protects the transmitted password. This could allow an attacker that is able to intercept the network traffic to obtain valid PLC credentials.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

This vulnerability in Siemens SIMATIC S7-300/400 CPUs, WinAC RTX, and SINUMERIK 840D sl devices allows an attacker with network traffic interception capability to capture plaintext or weakly protected passwords transmitted over port 102/tcp (ISO-TSAP). The authentication protocol fails to adequately encrypt credential data during transmission, enabling credential theft and subsequent unauthorized PLC access.

MitigationImplement network segmentation to restrict access to port 102/tcp, deploy VPN or encrypted tunnel solutions for remote access to PLCs, and monitor network traffic for suspicious interception attempts. Where available, apply vendor-supplied firmware updates that address the authentication weakness.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Simatic S7 300 Cpu 312 FirmwareOperating system
Affected:all versions
Simatic S7 300 Cpu 314 FirmwareOperating system
Affected:all versions
Simatic S7 300 Cpu 315 2 Dp FirmwareOperating system
Affected:all versions
Simatic S7 300 Cpu 315 2 Pn FirmwareOperating system
Affected:all versions
Simatic S7 300 Cpu 317 2 Pn FirmwareOperating system
Affected:all versions
Simatic S7 300 Cpu 317 2 Dp FirmwareOperating system
Affected:all versions
Simatic S7 300 Cpu 315f 2 Dp FirmwareOperating system
Affected:all versions
Simatic S7 300 Cpu 315f 2 Pn FirmwareOperating system
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify PLC model
    Connect to the PLC via Step 7 or TIA Portal and retrieve the CPU article number and model designation (e.g., 6ES7 312-xxxx). Confirm it matches one of the affected S7-300 models: 312, 314, 315-2 DP, 315-2 Pn, 317-2 Pn, 317-2 DP, 315f-2 DP, or 315f-2 Pn.
    Affected if The installed CPU is any of the listed S7-300 models.
  2. Check port 102/tcp status
    Use a network scanner (nmap, netstat) or PLC engineering software to verify whether port 102/tcp (ISO-TSAP) is open and listening on the PLC device.
    Affected if Port 102/tcp is open and accessible on the affected device.
  3. Verify network exposure of port 102
    Review firewall rules, VLAN segmentation, and network ACLs to determine if port 102/tcp is reachable from untrusted networks, DMZs, or the internet.
    Affected if Port 102/tcp is reachable from any network segment that includes untrusted or attacker-accessible hosts.
  4. Inspect PLC project for password protection
    Open the PLC hardware configuration in Step 7 or TIA Portal and check whether a password is configured under CPU properties under protection settings, and note whether protection level is set to 'Full' or 'Read-only'.
    Affected if A password is configured but the protection level is not set to the highest available setting, or if the project shows no password protection.
  5. Confirm network traffic interception risk
    Review network topology to determine if an attacker could position themselves to capture traffic on the same network segment as the PLC (through ARP spoofing, switch port mirroring, or network tap).
    Affected if The PLC's network segment is shared with other non-PLC systems or lacks network isolation, allowing potential traffic interception.

You are affected if you have any of the listed S7-300 CPU models with port 102/tcp accessible on your network, regardless of firmware version.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Implement network segmentation to restrict access to port 102/tcp, deploy VPN or encrypted tunnel solutions for remote access to PLCs, and monitor network traffic for suspicious interception attempts. Where available, apply vendor-supplied firmware updates that address the authentication weakness.

Fix this in Simatic S7 300 Cpu 312 Firmware Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing8.0 h
  • Review / QA4.0 h
36.0 hours of engineering $6,400
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-15791 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data