Security readout for executives and security teams
Plain-English summary
CVE-2021-36765 affects CODESYS EtherNetIP versions before 4.1.0.0. Certain EtherNet/IP requests may crash vulnerable runtime code through a null pointer dereference. For executives, the main concern is potential disruption to industrial control environments that rely on affected CODESYS runtime components.
Executive priority
Treat this as an operational resilience issue for CODESYS-based industrial systems. Priority should be higher where EtherNet/IP is reachable across networks or supports production-critical processes. Evidence is incomplete for severity and exploitation.
Technical view
The issue is a null pointer dereference in the vulnerable downloaded EtherNet/IP stack executed by the CODESYS Control runtime system. The source bundle does not provide CVSS, CWE, exploitability details, or runtime-specific impact beyond the crash condition.
Likely exposure
Exposure is likely limited to environments running CODESYS Control runtime systems with the downloaded CODESYS EtherNetIP stack before version 4.1.0.0. Internet or broadly reachable industrial network exposure would increase operational risk.
Exploitation context
The provided sources do not show active exploitation. The CVE is not listed as CISA KEV in the source bundle. The only described trigger is specific EtherNet/IP requests causing a null pointer dereference.
Researcher notes
The public bundle identifies the vulnerable component and version boundary but lacks CVSS, CWE, detailed impact, exploit status, and configuration prerequisites. Validation should focus on component versioning, runtime use of the downloaded stack, and network reachability.
Mitigation direction
- Upgrade CODESYS EtherNetIP to 4.1.0.0 or later where applicable.
- Review the CODESYS advisory for product-specific update guidance.
- Restrict EtherNet/IP access to trusted industrial network segments.
- Monitor control runtime stability for unexpected service failures.
- Prioritize exposed or production-critical controller environments first.
Validation and detection
- Inventory CODESYS Control runtimes using the EtherNet/IP stack.
- Confirm EtherNetIP component versions are not before 4.1.0.0.
- Verify EtherNet/IP services are not reachable from untrusted networks.
- Check vendor documentation for affected runtime combinations.
- Review logs for unexpected runtime crashes or resets.
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.
CVE-2021-36765 mapping review
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Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
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 and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://customers.codesys.com/index.php?eID=dumpFile&t=f&f=16806&token=3b0c51de5a6e35bccbb413ddaaa56551ca5490f6&download=CVE reference · x_refsource_CONFIRM
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.