How severe is CVE-2021-27852?

CVE-2021-27852 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-27852?

Affected package information for CVE-2021-27852 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2021-27852?

No fixed version has been published for CVE-2021-27852 yet. Monitor the advisory for updates, apply mitigations recommended by the vendor, and use O3 Security to track when a fix becomes available in your stack.

Is CVE-2021-27852 actively exploited in the wild?

Yes. There are 2 known exploit references for CVE-2021-27852, including 2 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-27852?

CVE-2021-27852 has an EPSS (Exploit Prediction Scoring System) score of 25.5%, placing it in the 96th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score warrants monitoring and prompt remediation.

Is CVE-2021-27852 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2021-27852 (Checkbox Survey Deserialization of Untrusted Data Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2022-04-11. CISA required all US federal civilian agencies to remediate this vulnerability by 2022-05-02. The required action was: Versions 6 and earlier for this product are end-of-life and must be removed from agency networks. Versions 7 and later are not considered vulnerable. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2021-27852?

CVE-2021-27852 is classified as Deserialization of Untrusted Data (CWE-502). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

Which products and versions are affected by CVE-2021-27852?

CVE-2021-27852 affects checkbox survey. Check the affected-products list on this page against your deployed version to confirm exposure.

When was CVE-2021-27852 published, and has it been updated?

CVE-2021-27852 was published on May 27, 2021 and was last updated on October 24, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV·Added 2022-04-11 — agencies required to remediate by 2022-05-02

CVE-2021-27852

CRITICAL

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

Published

May 27, 2021

Updated

Oct 24, 2025

Affected

0 pkgs

Patched

None yet

Exploits

2 known

EPSS Exploitation Probability

via FIRST.org ↗

25.5%probability of exploitation in next 30 days

Moderate Risk96th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

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.

Affected Products

1 product · 1 configurations

Application

surveycheckbox

< 7.0

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Deserialization of Untrusted Data vulnerability in CheckboxWeb.dll of Ch…

twitter.comAPIJul 2021

Deserialization of Untrusted Data vulnerability in CheckboxWeb.dll of Ch…

cisa.govCISAApr 2022

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2021-27852 in your stack?

O3 detects CVE-2021-27852 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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