Security readout for executives and security teams
Plain-English summary
This Siemens industrial-control vulnerability can let an unauthenticated network attacker crash affected PLCs or controllers through TCP port 102. Normal operation may require a device restart, creating production or process downtime risk. The issue affects specific SIMATIC and TIM product versions listed by Siemens/CVE.
Executive priority
Treat this as high priority for OT environments where affected controllers support production, safety-adjacent, or critical processes. The business risk is downtime, not data theft. Prioritize exposed or poorly segmented devices first, then schedule controlled updates and access restrictions.
Technical view
CVE-2021-37205 is a high-severity availability flaw in multiple Siemens SIMATIC PLC/controller products and TIM 1531 IRC. The CVSS 3.1 score is 7.5. An unauthenticated network attacker can trigger denial of service by sending specially prepared packets to 102/tcp. The listed weakness is CWE-401.
Likely exposure
Exposure is most likely where affected Siemens SIMATIC or TIM devices run vulnerable firmware/software and TCP/102 is reachable from untrusted or loosely segmented networks. Internet exposure would materially increase urgency, but the supplied sources do not state observed internet exploitation.
Exploitation context
The source bundle does not show CISA KEV listing or confirmed active exploitation. Exploitation requires network reachability to TCP/102 and no authentication. Impact is denial of service only per CVSS, but in OT environments availability loss can have operational consequences.
Researcher notes
Key validation is version and reachability, not payload testing. Affected ranges include S7-1200, S7-1500, Drive Controller, ET 200SP Open Controller, S7-1500 Software Controller, S7-PLCSIM Advanced, TIM 1531 IRC, and SIPLUS variants. Evidence supplied is sufficient for exposure triage but not for exploit prevalence.
Mitigation direction
- Upgrade affected products to versions outside the vulnerable ranges listed by Siemens/CVE.
- Restrict TCP/102 access to trusted engineering and operations hosts only.
- Review Siemens advisory SSA-838121 for product-specific update and hardening guidance.
- Plan restart windows because recovery from successful denial of service requires rebooting affected devices.
Validation and detection
- Inventory Siemens SIMATIC and TIM assets and record exact firmware or software versions.
- Identify devices exposing TCP/102 and map which networks can reach them.
- Compare versions against the affected ranges in the CVE record.
- Confirm updated devices run fixed versions or compensating network controls are enforced.
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
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-401: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-37205 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.
Missing Release of Memory after Effective Lifetime
Missing Release of Memory after Effective Lifetime represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.