CVE-2026-5426Known exploitationNetwork attack vector

Unauthenticated RCE via forged ViewState deserialization

Published Apr 16, 2026 · Updated Apr 16, 2026

ViewState deserialization in Digital Knowledge KnowledgeDeliver deployments before February 24, 2026 allows remote attackers to execute OS-level code. The standardized web.config embeds identical machineKey values, allowing a forged __VIEWSTATE HTTP parameter to pass validation and be deserialized by ASP.NET. Exploitation requires an accessible deployment whose default key remains unchanged and yields code execution in the IIS worker context.

CVSS severity9.1
Critical
EPSS probability1.01%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

ViewState deserialization in Digital Knowledge KnowledgeDeliver deployments before February 24, 2026 allows remote attackers to execute OS-level code. The standardized web.config embeds identical machineKey values, allowing a forged __VIEWSTATE HTTP parameter to pass validation and be deserialized by ASP.NET. Exploitation requires an accessible deployment whose default key remains unchanged and yields code execution in the IIS worker context.

The record

CVE
CVE-2026-5426
Published
Apr 16, 2026
Updated
Apr 16, 2026
Vendor
Digital Knowledge Co., Ltd.
Product
KnowledgeDeliver
Classifications
CWE-321, CWE-502, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <20260224

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Digital Knowledge Co., Ltd. · KnowledgeDeliverversion=0 <20260224

Published CVSS scores

9.1CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-321Use of Hard-coded Cryptographic Key
CWE-502Deserialization of Untrusted Data
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Reported exploitation

Technologies

Your stack

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Your stack

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