CVE-2021-27852

CRITICALNVD 9.89.8—
EchelonGraph scoreHIGH confidence

Score elevated to 9.8 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2022-04-11), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 9.8 retained for reference. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, epss, ghsa, nvd
Trending — 4 sources updated this weekExploited in the wild
9.8EG
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS PROB: 32%CVSS: 9.8Exploit: cisa kev · ssvc active · epss top5pctExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.8
EG Score
9.8(high)
EG Risk
99(Act)
EG Risk 99/100SSVC: Act

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation100% × 40%
Automatability100% × 15%
Action: Fix now — active exploitation, automatable, high impact.
EPSS PROB
32%
EPSS %ILE
98%
KEV
⚠ Exploited

Published

May 27, 2021

Last Modified

October 24, 2025

Advisory Details (2)

Auto-updated Sep 17, 2026
⚠️ Active exploitation confirmed. Patch available. Sources: cert, cisa.
cisa Patch Available🔴 Active Exploitation

Known Exploited Vulnerabilities Catalog | CISA

Known Exploited Vulnerabilities Catalog | CISA. Listed in CISA Known Exploited Vulnerabilities catalog.

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27852
cert🔴 Active Exploitation

VU#706695 - Checkbox Survey insecurely deserializes ASP.NET View State data

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

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 61× in last 7d / 256× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 924 total refreshes for this CVE.

  1. 2026-09-20 02:32 UTCGHSA enrichment
  2. 2026-09-19 22:43 UTCGHSA enrichment
  3. 2026-09-19 18:54 UTCEG score recompute
  4. 2026-09-19 18:54 UTCGHSA enrichment
  5. 2026-09-19 15:37 UTCEPSS rescore
  6. 2026-09-19 15:05 UTCGHSA enrichment
  7. 2026-09-19 11:14 UTCGHSA enrichment
  8. 2026-09-19 07:25 UTCGHSA enrichment
  9. 2026-09-19 03:36 UTCGHSA enrichment
  10. 2026-09-18 23:46 UTCGHSA enrichment
  11. 2026-09-18 19:57 UTCEG score recompute
  12. 2026-09-18 19:57 UTCGHSA enrichment
  13. 2026-09-18 19:23 UTCEPSS rescore
  14. 2026-09-18 19:20 UTCCISA KEV update
  15. 2026-09-18 16:07 UTCGHSA enrichment
  16. 2026-09-18 14:15 UTCCISA KEV update
  17. 2026-09-18 12:17 UTCGHSA enrichment
  18. 2026-09-18 08:28 UTCGHSA enrichment
  19. 2026-09-18 04:39 UTCGHSA enrichment
  20. 2026-09-18 00:50 UTCGHSA enrichment
  21. 2026-09-17 21:01 UTCEG score recompute
  22. 2026-09-17 21:01 UTCGHSA enrichment
  23. 2026-09-17 19:23 UTCEPSS rescore
  24. 2026-09-17 19:23 UTCEPSS rescore
  25. 2026-09-17 17:11 UTCGHSA enrichment
Show 75 more
  1. 2026-09-17 12:58 UTCGHSA enrichment
  2. 2026-09-17 09:09 UTCGHSA enrichment
  3. 2026-09-17 05:20 UTCGHSA enrichment
  4. 2026-09-17 01:31 UTCGHSA enrichment
  5. 2026-09-16 21:42 UTCGHSA enrichment
  6. 2026-09-16 17:52 UTCEG score recompute
  7. 2026-09-16 17:52 UTCGHSA enrichment
  8. 2026-09-16 14:10 UTCCISA KEV update
  9. 2026-09-16 14:05 UTCEPSS rescore
  10. 2026-09-16 14:03 UTCGHSA enrichment
  11. 2026-09-16 10:14 UTCGHSA enrichment
  12. 2026-09-16 06:24 UTCEG score recompute
  13. 2026-09-16 06:24 UTCGHSA enrichment
  14. 2026-09-16 02:35 UTCGHSA enrichment
  15. 2026-09-15 22:46 UTCGHSA enrichment
  16. 2026-09-15 18:54 UTCGHSA enrichment
  17. 2026-09-15 15:05 UTCGHSA enrichment
  18. 2026-09-15 11:16 UTCGHSA enrichment
  19. 2026-09-15 07:26 UTCGHSA enrichment
  20. 2026-09-15 03:36 UTCEG score recompute
  21. 2026-09-15 03:36 UTCGHSA enrichment
  22. 2026-09-15 03:06 UTCEPSS rescore
  23. 2026-09-15 03:06 UTCEPSS rescore
  24. 2026-09-14 23:46 UTCGHSA enrichment
  25. 2026-09-14 19:57 UTCGHSA enrichment
  26. 2026-09-14 19:24 UTCCISA KEV update
  27. 2026-09-14 16:08 UTCGHSA enrichment
  28. 2026-09-14 12:19 UTCGHSA enrichment
  29. 2026-09-14 08:30 UTCGHSA enrichment
  30. 2026-09-14 04:41 UTCGHSA enrichment
  31. 2026-09-14 00:52 UTCGHSA enrichment
  32. 2026-09-13 21:03 UTCGHSA enrichment
  33. 2026-09-13 17:13 UTCGHSA enrichment
  34. 2026-09-13 13:24 UTCGHSA enrichment
  35. 2026-09-13 09:34 UTCGHSA enrichment
  36. 2026-09-13 05:45 UTCGHSA enrichment
  37. 2026-09-13 01:56 UTCGHSA enrichment
  38. 2026-09-12 22:06 UTCGHSA enrichment
  39. 2026-09-12 18:17 UTCEG score recompute
  40. 2026-09-12 18:17 UTCGHSA enrichment
  41. 2026-09-12 14:57 UTCEPSS rescore
  42. 2026-09-12 14:28 UTCGHSA enrichment
  43. 2026-09-12 10:38 UTCGHSA enrichment
  44. 2026-09-12 06:49 UTCGHSA enrichment
  45. 2026-09-12 03:00 UTCGHSA enrichment
  46. 2026-09-11 23:11 UTCGHSA enrichment
  47. 2026-09-11 19:22 UTCGHSA enrichment
  48. 2026-09-11 18:49 UTCCISA KEV update
  49. 2026-09-11 15:33 UTCEG score recompute
  50. 2026-09-11 15:33 UTCGHSA enrichment
  51. 2026-09-11 14:49 UTCEPSS rescore
  52. 2026-09-11 11:43 UTCEG score recompute
  53. 2026-09-11 11:43 UTCGHSA enrichment
  54. 2026-09-11 09:33 UTCEPSS rescore
  55. 2026-09-11 07:54 UTCGHSA enrichment
  56. 2026-09-11 04:05 UTCGHSA enrichment
  57. 2026-09-11 00:15 UTCGHSA enrichment
  58. 2026-09-10 20:26 UTCGHSA enrichment
  59. 2026-09-10 19:28 UTCCISA KEV update
  60. 2026-09-10 16:37 UTCGHSA enrichment
  61. 2026-09-10 12:47 UTCEG score recompute
  62. 2026-09-10 12:47 UTCGHSA enrichment
  63. 2026-09-10 08:57 UTCGHSA enrichment
  64. 2026-09-10 05:06 UTCGHSA enrichment
  65. 2026-09-10 01:17 UTCGHSA enrichment
  66. 2026-09-09 21:27 UTCGHSA enrichment
  67. 2026-09-09 19:08 UTCCISA KEV update
  68. 2026-09-09 17:36 UTCGHSA enrichment
  69. 2026-09-09 13:47 UTCGHSA enrichment
  70. 2026-09-09 09:57 UTCGHSA enrichment
  71. 2026-09-09 06:08 UTCGHSA enrichment
  72. 2026-09-09 02:17 UTCGHSA enrichment
  73. 2026-09-08 22:26 UTCGHSA enrichment
  74. 2026-09-08 18:54 UTCCISA KEV update
  75. 2026-09-08 18:35 UTCGHSA enrichment

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Frequently asked(6)

What is CVE-2021-27852?
CVE-2021-27852 is a critical vulnerability published on May 27, 2021. 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.
When was CVE-2021-27852 disclosed?
CVE-2021-27852 was first published in the National Vulnerability Database on May 27, 2021, with the most recent update on October 24, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-27852 actively exploited?
Yes. CISA added CVE-2021-27852 to the Known Exploited Vulnerabilities catalog on April 11, 2022, affecting Checkbox Checkbox Survey. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2021-27852?
CVE-2021-27852 has a CVSS v3 base score of 9.8 (NVD).
Which products are affected by CVE-2021-27852?
CVE-2021-27852 affects Checkbox Checkbox Survey. The full affected-products list, including version ranges and fixed versions, is shown in the Affected Packages section of this page.
How do I remediate CVE-2021-27852?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-27852, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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