Security readout for executives and security teams
Plain-English summary
Concrete CMS through 8.5.5 could fetch update information over unencrypted HTTP. If that update JSON were tampered with in transit, the source description says it could lead to remote code execution. Public scoring details are absent, so urgency depends on whether your sites use affected Concrete CMS versions and that update path.
Executive priority
Prioritize this for any internet-facing or business-critical Concrete CMS site on 8.5.5 or earlier. The issue is potentially serious because the described impact is remote code execution, but public evidence in the bundle is limited and does not show known active exploitation.
Technical view
CVE-2021-40099 concerns Concrete CMS through 8.5.5. The reported issue is that update JSON was fetched using an HTTP scheme, creating a remote code execution risk. The bundle provides no CVSS vector, CWE, proof of active exploitation, or detailed vendor remediation text beyond references to a HackerOne report and 8.5.6 release notes.
Likely exposure
Organizations running Concrete CMS 8.5.5 or earlier are the stated exposure group. Risk is most relevant where servers perform update checks over networks where HTTP traffic can be intercepted or modified. The bundle does not identify affected CPEs, hosting models, or configuration prerequisites.
Exploitation context
The source bundle does not show CISA KEV listing or other evidence of active exploitation. The risk described requires tampering with update JSON fetched over HTTP, but the bundle does not provide exploit details, public weaponization status, or observed attack reports.
Researcher notes
Key gaps: no CVSS, CWE, CPE, detailed patch statement, or exploit telemetry in the bundle. Analysis should stay bounded to Concrete CMS through 8.5.5 and the HTTP update JSON RCE description. Use the HackerOne report and 8.5.6 release notes for deeper confirmation.
Mitigation direction
- Inventory Concrete CMS instances and identify versions 8.5.5 or earlier.
- Review Concrete CMS 8.5.6 release notes and vendor guidance for the supported fix path.
- Upgrade or apply vendor-directed remediation after confirming applicability.
- Limit administrative and update-related access to trusted networks where feasible.
- Monitor web servers for unexpected code changes or suspicious update activity.
Validation and detection
- Confirm each Concrete CMS instance version from administrative records or asset tooling.
- Check whether update metadata retrieval uses HTTP on affected deployments.
- Review change history around update checks for unexpected file modifications.
- Verify the vendor-advised fixed version or mitigation is applied.
- Document unresolved instances with owner, version, and remediation target date.
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.
Execution 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-2021-40099 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
- 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://hackerone.com/reports/982130CVE reference · x_refsource_MISC
- https://documentation.concretecms.org/developers/introduction/version-history/856-release-notesCVE 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.