Security readout for executives and security teams
Plain-English summary
CVE-2021-34586 is a denial-of-service flaw in the CODESYS V2 web server before V1.1.9.22. A remote unauthenticated request can crash or disrupt the web server component. The known impact is availability loss, not data theft or code execution, but availability matters in industrial environments.
Executive priority
Treat this as a high-priority availability risk for exposed industrial systems. Prioritize remediation where the CODESYS V2 web server is reachable from untrusted networks or supports operational visibility and control workflows.
Technical view
The issue is a CWE-476 null pointer dereference in the CODESYS V2 web server. CVSS 3.1 rates it 7.5 with network attack vector, low complexity, no privileges, no user interaction, and high availability impact only. Sources identify vulnerable CODESYS V2 web servers prior to V1.1.9.22.
Likely exposure
Exposure is most likely where CODESYS V2 web server instances are reachable over a network. Internet-facing or broadly reachable industrial control interfaces increase urgency. The provided sources do not identify specific downstream OEM devices or deployment counts.
Exploitation context
The source bundle does not show CISA KEV listing or confirmed active exploitation. The CVSS vector indicates remote unauthenticated denial-of-service is plausible, but no exploit status, payload, or observed campaign evidence is provided.
Researcher notes
Do not broaden scope beyond CODESYS V2 web server from the cited sources. The documented weakness is null pointer dereference causing denial of service. No confidentiality or integrity impact, active exploitation, or downstream product list is established in the bundle.
Mitigation direction
- Upgrade CODESYS V2 web server to V1.1.9.22 or later where applicable.
- Review the CODESYS advisory for device-specific update guidance.
- Restrict web server access to trusted management networks only.
- Remove unnecessary external exposure for CODESYS web interfaces.
- Monitor affected systems for unexpected web server crashes or restarts.
Validation and detection
- Inventory assets running CODESYS V2 web server.
- Confirm each instance is V1.1.9.22 or later.
- Identify any web server reachable from untrusted networks.
- Review operational logs for unexplained denial-of-service symptoms.
- Check vendor and device-maker guidance for embedded CODESYS components.
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-476: 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-2021-34586 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
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:H3.93.6Primary 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
Source materials
- CVE List V5 sourceCVE List V5
- https://customers.codesys.com/index.php?eID=dumpFile&t=f&f=16876&token=a3f1d937f95e7034879f4f2ea8e5a99b168256a7&download=CVE reference · x_refsource_CONFIRM
- https://www.tenable.com/security/research/tra-2021-47CVE reference · x_refsource_MISC
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.
NULL Pointer Dereference
NULL Pointer Dereference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.