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Known exploited · Checkbox

CVE-2021-27852: Checkbox Survey Deserialization of Untrusted Data Vulnerability

What it is

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

Added April 11, 2022Due May 2, 2022CISA KEV catalog 2026.10.01

Vendor
Checkbox
Product
Checkbox Survey
Added to KEV
April 11, 2022
CISA due date
May 2, 2022
Ransomware use
Unknown

What CISA requires

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.

Forensic triage

No

What to do now

  1. Find every instance of Checkbox Survey you run, including the forgotten ones, and check its version against the vendor advisory.
  2. Apply the vendor's fix or mitigation, before May 2, 2022 if you are bound by CISA's deadline, sooner if it faces the internet.
  3. Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.
  4. Until every instance is patched, block the attack at the edge: a WAF in blocking mode stops Java deserialization payloads.

References

CVE-2021-27852 in the National Vulnerability Database

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Block it at the edge while you patch

The Dome's WAF runs the OWASP Core Rule Set in blocking mode and stops Java deserialization payloads before they reach your application.

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Source: CISA Known Exploited Vulnerabilities Catalog (public domain), catalog version 2026.10.01.