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CVE-2026-13186 – Path Traversal to RCE – Telerik UI for ASP.NET AJAX prior to v2026.2.708

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Summary

CVE-2026-13186 is a path traversal vulnerability (CWE-22) in the file-based persistence storage provider of Progress Telerik UI for ASP.NET AJAX, affecting versions 2013.1.220 through 2026.2.519 (all releases prior to 2026.2.708). When the RadPersistenceManager component’s storage key is derived from user-controlled input, an unauthenticated remote attacker can manipulate the file path used to load persistence state, triggering attacker-controlled deserialization and achieving remote code execution (RCE) on the underlying server. The vulnerability carries a CVSS v3.1 base score of 8.1 (High).

Technical details

  • Root cause: The RadPersistenceManager component, when configured with a file-based storage provider, does not adequately restrict the pathname used to resolve the persistence state file. If the storage key is derived from user-controlled sources — such as query parameters, form fields, or cookies — an attacker can craft input containing path traversal sequences to influence which file on the server is loaded and deserialized.
  • Trigger conditions: Exploitation requires the application to use RadPersistenceManager with a file-based storage provider and a storage key sourced from attacker-controlled input. Applications that rely exclusively on server-side state to derive storage keys are not affected by this vulnerability.
  • Attack vector: Network-accessible and unauthenticated — no privileges or user interaction are required. Attack complexity is rated High (AC:H) because the vulnerable configuration (file-based storage with user-controlled keys) is non-default; however, it is a documented and used deployment pattern.
  • Impact: Successful exploitation allows the attacker to control which file the application deserializes, enabling arbitrary code execution on the server. Full compromise of confidentiality, integrity, and availability is possible. The attack potential is further increased when the attacker also has file upload capability within the server’s App_Data directory.

Affected software

  • Progress Telerik UI for ASP.NET AJAX — versions 2013.1.220 through 2026.2.519 (all versions prior to 2026.2.708)

Severity

  • CVSS v3.1 Base Score: 8.1 (High)
  • Vector String: 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 Progress Telerik UI for ASP.NET AJAX version 2026.2.708 (2026 Q2 SP1) or later, which contains the vendor-provided fix.
  • Workaround (if immediate upgrade is not feasible):
    • Ensure the RadPersistenceManager storage key is derived exclusively from server-side state — never from query parameters, form fields, or cookies.
    • As an additional defense-in-depth measure, relocate the RadAsyncUpload temporary folder outside the App_Data directory by configuring the Telerik.AsyncUpload.TemporaryFolder application setting. Note: this measure alone does not substitute for the primary mitigation above.

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

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