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Telerik Ui For Asp.net AjaxApplication · Progress

CVE-2026-6023

CRITICAL · 9.8 CVSS v3.1 Published 2026-04-22
Fix available
A fix is available. Upgrade to 2026.1.421 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In Progress® Telerik® UI for AJAX versions 2024.4.1114 through 2026.1.421, the RadFilter control is vulnerable to insecure deserialization when restoring filter state if the state is exposed to the client. If an attacker tampers with this state, a server-side remote code execution is possible.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The RadFilter control in Telerik UI for AJAX versions 2024.4.1114 through 2026.1.421 suffers from insecure deserialization during filter state restoration. When filter state is exposed to the client (the default behavior), an attacker can tamper with the serialized state data, which the server then deserializes without proper validation, leading to arbitrary code execution.

MitigationUpgrade Telerik UI for AJAX to a version beyond 2026.1.421 when available. If immediate patching is not possible, review whether RadFilter state exposure to the client can be disabled or protected through additional application-level validation.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Telerik Ui For Asp.net AjaxApplication
Affected:>= 2024.4.1114, < 2026.1.421

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Telerik UI for AJAX version
    Locate Telerik.Web.UI.dll in the application's bin folder or referenced assemblies. Right-click the DLL, select Properties, and view the File Version or Assembly Version. Alternatively, check the installed NuGet package version if using NuGet.
    Affected if The version falls within the range 2024.4.1114 to 2026.1.421 (inclusive).
  2. Verify RadFilter control is in use
    Search the codebase for references to 'RadFilter' in .aspx, .ascx, or code-behind files. Look for declarations like <telerik:RadFilter> or RadFilter instances in the application.
    Affected if RadFilter control is implemented in the application.
  3. Check if filter state exposure is enabled
    Examine the RadFilter configuration in the web.config or the RadFilter markup. Look for settings related to 'EnableState' or 'FilterState' that control whether filter state is serialized and exposed to the client. The default behavior exposes filter state to the client.
    Affected if Filter state is exposed to the client (the default behavior). This is required for the attack vector.
  4. Confirm client-side filter state handling
    Use browser developer tools to inspect network requests from pages using RadFilter. Look for query parameters or hidden form fields containing serialized filter state data (often Base64-encoded or JSON).
    Affected if Serialized filter state data is visible in client-server communication.

The environment is affected if Telerik UI for AJAX version is between 2024.4.1114 and 2026.1.421, RadFilter control is in use, and filter state is exposed to the client (the default configuration).

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2026.1.421 or later
Fixed in 2026.1.421
Interim mitigation

Upgrade Telerik UI for AJAX to a version beyond 2026.1.421 when available. If immediate patching is not possible, review whether RadFilter state exposure to the client can be disabled or protected through additional application-level validation.

Recommended fix High confidence

Telerik UI for ASP.NET AJAX version 2026.1.421 or later

  1. 1. Identify all projects in your solution that reference Telerik UI for ASP.NET AJAX.
  2. 2. Use NuGet Package Manager or manually edit the .csproj file to update the Telerik.UI.for.AspNet.Ajax package reference.
  3. 3. Update the version from your current vulnerable version to 2026.1.421 or later.
  4. 4. Restore the updated NuGet packages.
  5. 5. Rebuild the solution to ensure compatibility.
  6. 6. Test the RadFilter control functionality to verify the fix works correctly.
  7. 7. Deploy to staging and verify no regressions before production deployment.
Caveat Review Telerik's release notes for version 2026.1.421 for any breaking changes or breaking changes between your current version and the target version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Telerik Ui For Asp.net Ajax Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing8.0 h
  • Review / QA4.0 h
18.0 hours of engineering $3,080
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-6023 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data