Security readout for executives and security teams
Plain-English summary
This Siemens PLC vulnerability can let an unauthenticated network attacker crash affected controllers by sending specially prepared traffic to TCP port 102. Recovery requires restarting the affected device, so the business risk is operational interruption, not data theft. Sites using exposed Siemens SIMATIC or TIM devices in the listed firmware ranges should treat this as high priority.
Executive priority
Prioritize remediation for production controllers, safety-adjacent processes, and any site with remote or cross-network access to TCP/102. This is not a data breach issue, but it can stop industrial operations and require manual recovery. Patch planning should be coordinated with operations windows.
Technical view
CVE-2021-37185 affects multiple Siemens SIMATIC controller families and TIM 1531 IRC variants. The issue is CWE-672 and has CVSS 3.1 score 7.5, with network attack vector, low complexity, no privileges, and high availability impact. The source bundle states denial of service over 102/tcp and restoration only after device restart.
Likely exposure
Exposure is most likely in industrial networks running affected Siemens SIMATIC S7-1200, S7-1500, Drive Controller, Software Controller, PLCSIM Advanced, ET 200SP Open Controller, or TIM 1531 IRC versions. Risk rises sharply where TCP/102 is reachable from untrusted IT networks, vendors, remote access paths, or the internet.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. They do indicate unauthenticated network reachability and low attack complexity, making exploitation plausible where port 102/tcp is exposed. Evidence supports denial of service only; it does not support confidentiality or integrity impact.
Researcher notes
Do not assume every Siemens PLC is affected; validate exact product family and firmware range. The evidence identifies availability-only impact and required restart recovery. No source in the bundle establishes public exploit code, active exploitation, or broader impacts beyond denial of service over TCP/102.
Mitigation direction
- Upgrade affected Siemens products outside the vulnerable version ranges named in the advisory.
- Restrict TCP/102 access to trusted engineering and control network hosts only.
- Segment PLC networks from corporate IT, remote access, and internet-facing paths.
- Review Siemens SSA-838121 for product-specific updates and compensating controls.
- Prepare operational restart procedures for affected controllers until remediation is complete.
Validation and detection
- Inventory Siemens controller models and firmware versions against the affected version ranges.
- Verify whether TCP/102 is reachable from non-control-network segments.
- Check firewall, VPN, jump host, and vendor access paths to PLC networks.
- Confirm remediation status against Siemens SSA-838121 and local asset records.
- Review incident logs for unexplained PLC denial-of-service events requiring restart.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
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CWE-672: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-37185 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C
Source materials
- CVE List V5 sourceCVE List V5
- https://cert-portal.siemens.com/productcert/pdf/ssa-838121.pdfCVE reference
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Operation on a Resource after Expiration or Release
Operation on a Resource after Expiration or Release represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.