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CVE-2026-19219 – Remote Code Execution via RadEditor File Browser Tampering – Telerik UI for ASP.NET

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Summary

CVE-2026-19219 is an insufficient integrity protection vulnerability in Telerik UI for ASP.NET AJAX’s RadEditor component. Attackers who possess or recover the application’s encryption key material can tamper with dialog request parameters used by RadEditor’s built-in file browser to alter the folders it reads from, writes to, and uploads into, potentially resulting in remote code execution. The flaw carries a CVSS v3.1 base score of 8.1 (High).

Technical details

  • Root cause: insufficient integrity protection of dialog request parameters used by RadEditor’s built-in file browser dialogs, allowing tampering with upload/read/write folder paths (CWE-345: Insufficient Verification of Data Authenticity; CWE-434: Unrestricted Upload of File with Dangerous Type).
  • Trigger conditions: the application must use RadEditor’s built-in file browser dialogs, and either a custom DialogParametersEncryptionKey is configured or the ASP.NET machineKey uses static (non-AutoGenerate) values, and this key material has been exposed or recovered by the attacker.
  • Attack vector: Network (AV:N), with High attack complexity (AC:H) reflecting the prerequisite of obtaining valid encryption key material; no privileges or user interaction are required.
  • Impact: successful exploitation allows manipulation of file browser upload/access paths, which can lead to placement of malicious files in executable web-accessible directories and ultimately remote code execution; impact is rated High for confidentiality, integrity, and availability.

Affected software

  • Progress Telerik UI for ASP.NET AJAX, versions 2011.2.712 through 2026.2.708 (2026 Q2 SP2)

Severity

  • CVSS v3.1 Base Score: 8.1 (High)
  • Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Upgrade to Telerik UI for ASP.NET AJAX version 2026.3.812 (2026 Q3) or later.
  • If patching is not immediately possible:
    • Restrict the application pool’s write permissions to only what is required within the application root.
    • Disable script execution in any writable directories used for uploads.
    • Remove RadEditor controls or disable file browser functionality where not required.
    • If dialog functionality is unnecessary, disable Telerik.Web.UI.DialogHandler.aspx via web.config configuration.
    • Ensure machineKey and any custom DialogParametersEncryptionKey values are not exposed, and rotate them if compromise is suspected.

How IONIX identifies potentially affected assets

IONIX matches the following signals against data already collected when it crawled the asset; identifying the technology sends no request beyond that crawl.

  • Raw response body: Telerik.Web.UI.WebResource.axd
  • URL of a loaded script: Telerik.Web.UI.WebResource.axd

References

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Zero-Days to Shrink MTTR

1

Map your entire attack surface (continously)

IONIX uses multi-factor discovery methods, including DNS analysis, certificate mapping, metadata inspection, and more, to automatically map every internet-facing asset across your environment. This includes cloud instances, third-party platforms, shadow IT, and even forgotten infrastructure that traditional tools miss.

2

Monitor for new CVEs

Dozens of threat intel feeds using agentic technology are continuously analyzed to detect the appearance of proof-of-concept code, exploit kits, and indicators of active targeting. IONIX goes further by applying AI to proactively evaluate whether emerging vulnerabilities are likely to be exploited, even before PoCs go public.

3

Identify Potential External Exposures

Not all CVEs matter. IONIX filters vulnerabilities by asking attacker-centric questions: Can it be reached from the internet? Does it require authentication? Is it being exploited in the wild? This dramatically reduces noise and focuses teams on threats that can actually be weaponized.

4

Create Safe, Scalable Exploit Validations

IONIX transforms real-world PoCs into safe, non-intrusive test payloads that can be run in production environments without disruption. These simulations are precisely targeted to the systems that are vulnerable, ensuring rapid validation without unnecessary load.

5

Execute Exploit Validations

By combining context about software stack, versioning, exposure status, and reachability, IONIX ensures that only the right payloads are executed against the right assets, maximizing efficiency and minimizing risk.

6

Drive Fast and Actionable Remediation

Results are routed through integrations with ticketing, SOAR, and SIEM tools. Issues are written in plain language, bundled into remediation clusters, and prioritized based on asset criticality, exploitability, and blast radius. This shortens mean time to remediation (MTTR) and empowers teams to act with confidence.

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