Siemens SIMATIC Drive Controller family: Missing Release of Memory after Effective Lifetime (CVE-2021-37205)
Published Sources: Siemens ProductCERT, CVE.org
What is affected, what to do
A vulnerability has been identified in SIMATIC Drive Controller family (All versions >= V2.9.2 < V2.9.4), SIMATIC ET 200SP Open Controller CPU 1515SP PC2 (incl. SIPLUS variants) (All versions >= V21.9 < V21.9.4), SIMATIC S7-1200 CPU family (incl.
The available sources name no fixed version. Check the vendor guidance in the references below.
- Affected
- Siemens SIMATIC Drive Controller family
eq All versions >= V2.9.2 < V2.9.4..All versions >= V2.9.2 < V2.9.4 - Siemens SIMATIC ET 200SP Open Controller CPU 1515SP PC2 (incl. SIPLUS variants)
eq All versions >= V21.9 < V21.9.4..All versions >= V21.9 < V21.9.4 - Siemens SIMATIC S7-1200 CPU family (incl. SIPLUS variants)
eq All versions >= V4.5.0 < V4.5.2..All versions >= V4.5.0 < V4.5.2 - Siemens SIMATIC S7-1500 CPU family (incl. related ET200 CPUs and SIPLUS variants)
eq All versions >= V2.9.2 < V2.9.4..All versions >= V2.9.2 < V2.9.4 - Siemens SIMATIC S7-1500 Software Controller
eq All versions >= V21.9 < V21.9.4..All versions >= V21.9 < V21.9.4 - Siemens SIMATIC S7-PLCSIM Advanced
eq All versions >= V4.0 < V4.0 SP1..All versions >= V4.0 < V4.0 SP1 - Siemens SIPLUS TIM 1531 IRC
eq All versions < V2.3.6..All versions < V2.3.6 - Siemens TIM 1531 IRC
eq All versions < V2.3.6..All versions < V2.3.6
- Siemens SIMATIC Drive Controller family
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Metrics
7.5
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: Vendor (CNA), CVSS v3
7.5
CVSS v3
Severity High on the scale from 0 to 10.
Source: Siemens ProductCERT, CVE.org
1.6 %
EPSS score
Moderate — model estimates 1-10% exploitation likelihood.
Source: FIRST EPSS, percentile 76.3
Show all metrics
- Severity
- High
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 84.50 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 7.5 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 7.5
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 1.6 %
- Moderate — model estimates 1-10% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 76.3
- High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
- CISA assessment (SSVC)
- Exploitation: none known · automatable · Technical impact: partial
- Source: CISA Vulnrichment, as of 18 April 2025
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-401
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
A vulnerability has been identified in SIMATIC Drive Controller family (All versions >= V2.9.2 < V2.9.4), SIMATIC ET 200SP Open Controller CPU 1515SP PC2 (incl. SIPLUS variants) (All versions >= V21.9 < V21.9.4), SIMATIC S7-1200 CPU family (incl. SIPLUS variants) (All versions >= V4.5.0 < V4.5.2), SIMATIC S7-1500 CPU family (incl. related ET200 CPUs and SIPLUS variants) (All versions >= V2.9.2 < V2.9.4), SIMATIC S7-1500 Software Controller (All versions >= V21.9 < V21.9.4), SIMATIC S7-PLCSIM Advanced (All versions >= V4.0 < V4.0 SP1), SIPLUS TIM 1531 IRC (All versions < V2.3.6), TIM 1531 IRC (All versions < V2.3.6). An unauthenticated attacker could cause a denial-of-service condition in a PLC when sending specially prepared packets over port 102/tcp. A restart of the affected device is needed to restore normal operations.
Source: siemens_advisory, NVD (NIST), cvelistv5
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| Siemens | SIMATIC Drive Controller family |
|
|
| Siemens | SIMATIC ET 200SP Open Controller CPU 1515SP PC2 (incl. SIPLUS variants) |
|
|
| Siemens | SIMATIC S7-1200 CPU family (incl. SIPLUS variants) |
|
|
| Siemens | SIMATIC S7-1500 CPU family (incl. related ET200 CPUs and SIPLUS variants) |
|
|
| Siemens | SIMATIC S7-1500 Software Controller |
|
|
| Siemens | SIMATIC S7-PLCSIM Advanced |
|
|
| Siemens | SIPLUS TIM 1531 IRC |
|
|
| Siemens | TIM 1531 IRC |
|
|
| siemens | simatic_s7-1500_software_controller |
|
|
Vendors and products
- Siemens Simatic Drive Controller CPU 1504d Tf Firmware
- Siemens Simatic Drive Controller CPU 1507d Tf Firmware
- Siemens Simatic Drive Controller Family
- Siemens Siemens SIMATIC ET 200SP OPEN CONTROLLER CPU 1515SP PC2 Firmware
- Siemens Simatic Et 200sp Open Controller CPU 1515sp Pc2 (incl. Siplus Variants)
- Siemens Siemens SIMATIC S7-1200 CPU 1211C Firmware
- Siemens Siemens SIMATIC S7-1200 CPU 1212C Firmware
- Siemens Simatic S7-1200 CPU 1212fc Firmware
- Siemens Siemens SIMATIC S7-1200 CPU 1214C Firmware
- Siemens Simatic S7-1200 CPU 1214fc Firmware
- Siemens Siemens SIMATIC S7-1200 CPU 1215C Firmware
- Siemens Simatic S7-1200 CPU 1215fc Firmware
Affected operating systems
| Other | siemens | simatic_drive_controller_cpu_1504d_tf_firmware | — |
| Other | siemens | simatic_drive_controller_cpu_1507d_tf_firmware | — |
| Other | siemens | simatic_et_200sp_open_controller_cpu_1515sp_pc2_firmware | — |
| Other | siemens | simatic_s7-1200_cpu_1211c_firmware | — |
| Other | siemens | simatic_s7-1200_cpu_1212c_firmware | — |
| Other | siemens | simatic_s7-1200_cpu_1212fc_firmware | — |
| Other | siemens | simatic_s7-1200_cpu_1214c_firmware | — |
| Other | siemens | simatic_s7-1200_cpu_1214fc_firmware | — |
| Other | siemens | simatic_s7-1200_cpu_1215c_firmware | — |
| Other | siemens | simatic_s7-1200_cpu_1215fc_firmware | — |
| Other | siemens | simatic_s7-1200_cpu_1217c_firmware | — |
| Other | siemens | simatic_s7-1500_cpu_1510sp-1_firmware | — |
| Other | siemens | simatic_s7-1500_cpu_1510sp_firmware | — |
| Other | siemens | simatic_s7-1500_cpu_1511-1_firmware | — |
| Other | siemens | simatic_s7-1500_cpu_1511c-1_firmware | — |
| Other | siemens | simatic_s7-1500_cpu_1511f-1_firmware | — |
| Other | siemens | simatic_s7-1500_cpu_1511t-1_firmware | — |
| Other | siemens | simatic_s7-1500_cpu_1511tf-1_firmware | — |
| Other | siemens | simatic_s7-1500_cpu_1512c-1_firmware | — |
| Other | siemens | simatic_s7-1500_cpu_1512sp-1_firmware | — |
| Other | siemens | simatic_s7-1500_cpu_1512spf-1_firmware | — |
| Other | siemens | simatic_s7-1500_cpu_1513-1_firmware | — |
| Other | siemens | simatic_s7-1500_cpu_1513f-1_firmware | — |
| Other | siemens | simatic_s7-1500_cpu_1513r-1_firmware | — |
Weakness classes (CWE)
CWE-401Missing Release of Memory after Effective Lifetime
Variant
The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.
Entry at MITRE CWE-401
References & sources
- Siemens ProductCERTproductcert/pdf/ssa-838121.pdfPatch, Vendor advisory
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<a href="https://intel.neosec.eu/en/cve/CVE-2021-37205"><img src="https://intel.neosec.eu/badge/cve/CVE-2021-37205.svg?lang=en" alt="CVE-2021-37205 – NEOSEC Intel" height="20"></a>