Security readout for executives and security teams
Plain-English summary
Checkbox Survey before version 7 has a critical flaw that can let an unauthenticated remote attacker run code on the server. Because CISA lists it in KEV, treat exposed legacy installations as urgent until proven remediated.
Executive priority
Treat this as an immediate remediation item for any legacy Checkbox Survey system. The combination of unauthenticated remote code execution, critical severity, and KEV listing creates material business risk.
Technical view
CVE-2021-27852 is a CWE-502 unsafe deserialization issue in CheckboxWeb.dll. The CVSS 3.1 score is 9.8 with network access, low complexity, no privileges, and no user interaction required, with high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is limited to Checkbox Survey deployments running versions prior to 7. Risk is highest where the application is reachable from the internet or broadly reachable inside the network.
Exploitation context
CISA KEV status indicates known exploitation. The provided sources do not describe exploit chains, threat actors, affected environments beyond Checkbox Survey prior to 7, or detailed exploitation mechanics.
Researcher notes
The source bundle supports critical severity, unsafe deserialization, unauthenticated remote code execution, affected versions prior to 7, and KEV status. It does not provide patch notes, proof-of-concept details, telemetry, or vendor-specific hardening steps.
Mitigation direction
- Identify all Checkbox Survey deployments and their versions.
- Prioritize removing or upgrading versions prior to 7.
- Check Checkbox vendor guidance for supported fixed releases and upgrade instructions.
- Restrict network access to legacy instances while remediation is planned.
- Retire unsupported Checkbox Survey deployments if upgrade is not available.
Validation and detection
- Confirm no Checkbox Survey instance is below version 7.
- Verify public-facing asset inventories include Checkbox Survey hosts.
- Check vulnerability scanner findings against actual installed versions.
- Review CISA KEV tracking for due-date and remediation evidence.
- Document compensating controls for any instance awaiting upgrade.
Public sources used
Michael Williams reviewed this cited source version on .
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-502: Code execution behavior lookup
Code execution and unsafe deserialization weaknesses often justify reviewing execution behavior and process 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-2021-27852 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
- 9.8 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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.
CISA KEV status
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:U/C:H/I:H/A:H3.95.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.kb.cert.org/vuls/id/706695CVE reference
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27852CVE reference · government-resource
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.
Deserialization of Untrusted Data
Deserialization of Untrusted Data represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.