Security readout for executives and security teams
Plain-English summary
ZendTo file drop-off portals in affected versions can let an unauthenticated internet user run operating-system commands on the server. The issue is critical because it requires no login or user interaction and could compromise confidentiality, integrity, and availability.
Executive priority
Treat this as urgent for any public ZendTo deployment. No authentication is required, and successful exploitation could lead to full server compromise. Prioritize inventory and upgrade before routine work.
Technical view
CVE-2021-47667 is CWE-78 OS command injection in lib/NSSDropoff.php. ZendTo 5.24-3 through 6.x before 6.10-7 accepts shell metacharacters in the tmp_name parameter during POST /dropoff file submission, allowing unauthenticated remote command execution.
Likely exposure
Exposure is likely where ZendTo file drop-off is internet-facing and running 5.24-3 through 6.x before 6.10-7. The source bundle does not provide CPEs or deployment prevalence.
Exploitation context
The CVE describes unauthenticated remote command execution with CVSS 10. The bundle marks KEV false and provides no cited evidence of active exploitation, so exploitation should not be stated as observed.
Researcher notes
The source bundle is specific about vulnerable code path, parameter, request route, and fixed version boundary. It does not include exploit telemetry, CPE mappings, or detailed vendor remediation notes beyond versions before 6.10-7.
Mitigation direction
- Identify all ZendTo instances and their deployed versions.
- Upgrade affected ZendTo deployments to 6.10-7 or later where applicable.
- Restrict public access to ZendTo until remediation is complete.
- Review vendor and project guidance for any additional configuration or cleanup steps.
Validation and detection
- Confirm whether any exposed ZendTo instance is below version 6.10-7.
- Verify the /dropoff route is not publicly reachable on unremediated systems.
- Review web and application logs for suspicious /dropoff activity.
- Check hosts for unexpected process execution or file changes around drop-off requests.
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-78: Command execution behavior lookup
Command injection weaknesses can lead defenders to review execution techniques and command interpreter 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-2021-47667 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
- Critical
- CVSS
- 10 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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.
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:C/C:H/I:H/A:H3.96Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
10CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://projectblack.io/blog/zendto-nday-vulnerabilities/CVE reference
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.
Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.