Security readout for executives and security teams
Plain-English summary
This issue concerns CheckMK Enterprise Edition’s ability to upload MKP extension packages through the web management console. The source says this can allow remote code execution, but only through access to the management interface using administrator privileges or a hijacked administrator session. The vendor reportedly considers this administrator package behavior intentional.
Executive priority
Treat this as high priority for environments where CheckMK administers critical monitoring infrastructure. Focus on administrative access control, management console exposure, and package provenance rather than assuming an unauthenticated internet-wide exploit.
Technical view
CVE-2021-40905 is reported as CWE-434 affecting CheckMK Enterprise Edition versions 1.5.0 through 2.0.0p9. The issue involves insufficient sanitization of uploaded .mkp extension packages, enabling code execution through the web console. The description conflicts with the CVSS vector: narrative requires administrator access, while the vector lists PR:N/UI:R.
Likely exposure
Exposure is most likely where CheckMK Enterprise Edition 1.5.0 to 2.0.0p9 is deployed and the web management console is reachable by administrators or vulnerable to administrator session theft.
Exploitation context
No CISA KEV listing is provided, and the bundle does not prove active exploitation. The provided GitHub reference suggests public technical discussion exists, but the CVE text says exploitation requires valid administrator access or a hijacked administrator session.
Researcher notes
Evidence is incomplete on a vendor patch because the CVE notes the vendor views this as intended administrator behavior. Validate the privilege requirement carefully because the narrative and CVSS vector disagree. Avoid treating this as active exploitation without separate evidence.
Mitigation direction
- Identify CheckMK Enterprise deployments and versions in scope.
- Restrict web management console access to trusted administrative networks.
- Enforce strong administrator authentication and session protections.
- Allow MKP installation only from trusted sources and administrators.
- Review Checkmk vendor guidance before changing package behavior.
- Upgrade or remediate only according to current vendor-supported guidance.
Validation and detection
- Confirm whether CheckMK Enterprise 1.5.0 to 2.0.0p9 is present.
- Verify who can access the web management interface.
- Review administrator account and session security controls.
- Audit MKP upload and installation history for unexpected activity.
- Check vendor documentation for intended MKP behavior and controls.
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-434: File access and web shell behavior lookup
File traversal and upload weaknesses can lead teams to review file, web shell, execution, and collection telemetry. 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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-40905 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
- 8.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/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.
SSVC decision data
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:R/S:U/C:H/I:H/A:H2.85.9CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/Edgarloyola/CVE-2021-40905CVE reference, mitre
- https://docs.checkmk.com/latest/en/mkps.htmlCVE reference, mitre
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.