Security readout for executives and security teams
Plain-English summary
This Siemens PLC vulnerability can let an unauthenticated network attacker disrupt affected SIMATIC S7-400, S7-410, and SIPLUS controllers. The impact is availability: crafted traffic to TCP port 102 can force a denial-of-service condition, and normal operation requires a restart. For industrial environments, treat this as an operational continuity risk.
Executive priority
Prioritize in environments where these Siemens controllers support critical production, safety, or utility processes. The risk is outage, not data theft, but recovery may require manual operational intervention.
Technical view
CVE-2021-40368 affects listed Siemens SIMATIC and SIPLUS CPU families. Devices improperly handle specially crafted packets sent to 102/tcp, mapped to CWE-119. CVSS 3.1 is 7.5 with network attack vector, low complexity, no privileges, no user interaction, and high availability impact only.
Likely exposure
Exposure is most likely in OT networks using affected Siemens S7-400, S7-410, or SIPLUS CPUs where TCP/102 is reachable. Internet exposure is not stated in the sources and should not be assumed without asset evidence.
Exploitation context
The bundle does not show CISA KEV listing or other evidence of active exploitation. The vulnerability is plausibly disruptive because exploitation requires only network reachability to TCP/102 and can require a device restart to recover.
Researcher notes
The source bundle gives affected models, version thresholds, port, impact, and CVSS details, but not full Siemens remediation text. Avoid assuming exploit availability or universal patch coverage beyond the listed non-affected version thresholds.
Mitigation direction
- Identify affected Siemens CPU models and firmware versions across OT inventories.
- Upgrade affected products to non-affected versions where Siemens lists fixed version thresholds.
- For products listed as all versions, check Siemens SSA-557541 for current vendor guidance.
- Restrict TCP/102 access to trusted engineering and operations networks only.
- Prepare operational recovery plans for controller restart scenarios.
Validation and detection
- Confirm whether any listed SIMATIC or SIPLUS CPU models are deployed.
- Compare firmware versions against the affected version ranges in the CVE record.
- Review network paths to determine who can reach TCP/102 on controllers.
- Check monitoring for unexplained controller denial-of-service or restart events.
- Document compensating controls where upgrades are not immediately possible.
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-119: 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-2021-40368 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-557541.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.
Improper Restriction of Operations within the Bounds of a Memory Buffer
Improper Restriction of Operations within the Bounds of a Memory Buffer represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.