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 Jul 28, 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 45× in last 7d / 227× 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 464 total refreshes for this CVE.

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