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Fencer Vulns
critical 9.8

CVE-2021-27852 kev in the critical feed json

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

published 2021-05-27 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-14590

cvss
9.8
version 3.1, CNA
cisa kev
Exploited
added 2022-04-11
epss
30.3%
EPSS 30.3% chance of exploitation in 30 days, percentile 98%
public exploits
0
none known

Summary

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.

Patch / fix

cisa required action 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.

  • Checkbox Survey 7

Timeline

  1. Published
  2. Added to CISA KEV
  3. CISA patch deadline
  4. CISA SSVC: exploitation active

Known exploited

Added
4 y ago
Patch by
2022-05-02 (4 y ago)
Ransomware
Not known
Required action
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.
Vendor, product
Checkbox, Checkbox Survey
CISA name
Checkbox Survey Deserialization of Untrusted Data Vulnerability

CISA SSVC

Exploitation
Active, exploited in the wild
Automatable
yes
Technical impact
total
Assessed
21 mo ago

Exploit prediction

30.26% chance of exploitation in the next 30 days, higher than 98% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Affected products

  • Checkbox Survey

Classification

Weakness
  • CWE-502 Deserialization of Untrusted Data

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.