Security readout for executives and security teams
Plain-English summary
CVE-2021-28976 is reported as remote code execution in GetSimpleCMS before 3.3.16 through PHAR file handling in admin/upload.php. For a business, the concern is that an affected CMS could allow server-side code execution if the vulnerable upload path is reachable. The source bundle does not provide CVSS, authentication details, or confirmed exploitation.
Executive priority
Prioritize remediation where GetSimpleCMS supports public websites or sensitive workflows. Remote code execution on a CMS can affect site integrity and hosting infrastructure, but urgency should reflect confirmed version exposure because exploit details are incomplete.
Technical view
The CVE record describes RCE in GetSimpleCMS versions before 3.3.16 via PHAR files uploaded through admin/upload.php. The available metadata does not identify CWE, CVSS scoring, exact prerequisites, or exploit maturity. Treat exposure as version- and route-dependent until confirmed against the referenced issue and deployed application configuration.
Likely exposure
Likely exposure is GetSimpleCMS installations older than 3.3.16 where admin/upload.php is present and reachable. The bundle does not prove unauthenticated access or broader product impact.
Exploitation context
CISA KEV status is false, and the supplied sources do not claim active exploitation. Public issue reference exists, but the bundle does not include exploit reliability, prerequisites, or observed attacks.
Researcher notes
Key gaps are CVSS, CWE, authentication requirements, vulnerable code path details, and exploit status. The title and description align on PHAR upload handling in admin/upload.php before 3.3.16, but deeper validation requires the referenced GitHub issue and local application review.
Mitigation direction
- Upgrade GetSimpleCMS installations to 3.3.16 or later.
- Review the linked GetSimpleCMS issue for vendor-specific fix context.
- Restrict administrative upload access according to existing CMS hardening guidance.
- Prioritize externally reachable or business-critical CMS instances first.
Validation and detection
- Inventory all GetSimpleCMS instances and record exact versions.
- Confirm no production instance runs a version before 3.3.16.
- Review access logs for admin/upload.php activity and PHAR upload attempts.
- Verify upload handling after update using approved defensive test procedures.
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.
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-2021-28976 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://github.com/GetSimpleCMS/GetSimpleCMS/issues/1335CVE 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.