Security readout for executives and security teams
Plain-English summary
Concrete CMS installations through 8.5.5 may allow an attacker to delete arbitrary files through a PHP deserialization weakness. File deletion can disrupt site availability or damage application data, depending on what files the vulnerable code can reach. Public severity scoring is not provided in the source bundle.
Executive priority
Treat this as a targeted remediation item for any Concrete CMS estate. The business risk is service disruption or data loss through file deletion, but urgency is limited by missing severity, exploitability, and active exploitation evidence in the provided sources.
Technical view
CVE-2021-40102 describes arbitrary file deletion in Concrete CMS through 8.5.5 via PHAR deserialization triggered through is_dir, involving PHP object injection and the __wakeup magic method. The provided record does not include CVSS, CWE, authentication requirements, or full attack preconditions.
Likely exposure
Exposure is most likely for organizations running Concrete CMS version 8.5.5 or earlier. The source bundle does not identify specific editions, hosting configurations, required privileges, or affected components beyond Concrete CMS through 8.5.5.
Exploitation context
The source bundle does not show CISA KEV listing or cited evidence of active exploitation. A HackerOne report is referenced, but the provided bundle does not include enough detail to confirm exploit maturity, authentication needs, or public weaponization.
Researcher notes
Key gaps remain: no CVSS vector, no CWE assignment, no authentication context, no affected component path, and no exploitation status. Validate against the HackerOne report and Concrete CMS release notes before assigning final risk or exposure scope.
Mitigation direction
- Inventory Concrete CMS versions and flag 8.5.5 or earlier for review.
- Review Concrete CMS 8.5.6 release notes and vendor guidance for remediation.
- Upgrade to a vendor-supported fixed release when vendor guidance confirms applicability.
- Restrict administrative and file-handling access until remediation is complete.
- Ensure recent, tested backups exist before and after remediation.
Validation and detection
- Confirm the deployed Concrete CMS version on each instance.
- Check whether instances are version 8.5.5 or earlier.
- Review web server and application logs for unexpected file deletion symptoms.
- Verify vendor release notes map the fix to CVE-2021-40102.
- After remediation, confirm the CMS reports the expected fixed version.
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.
File access behavior lookup
The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-40102 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/921288CVE 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.