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CVE-2026-13183 – Cryptographic Timing Oracle Exposes Protected Metadata – Progress Telerik UI for…

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Summary

CVE-2026-13183 is a high-severity cryptographic timing oracle vulnerability in the RadAsyncUpload component of Progress Telerik UI for ASP.NET AJAX, affecting all versions from 2010.1.309 through 2026.2.707. By exploiting measurable timing differences during upload metadata processing, an unauthenticated remote attacker can recover cryptographically protected metadata values, resulting in high confidentiality impact (CVSS 7.5). Progress has released a fix in version 2026.2.708 (2026 Q2 SP1).

Technical details

  • Root cause: The RadAsyncUpload component’s metadata processing routine leaks cryptographic validity through observable differences in server response timing (CWE-208: Observable Timing Discrepancy / CAPEC-385: Covert Timing Channel). These timing variations allow an attacker to distinguish valid from invalid cryptographic metadata, functioning as a timing oracle.
  • Trigger conditions: An attacker submits crafted upload requests to the RadAsyncUpload HTTP handler. Differences in server processing time depending on cryptographic validation outcomes disclose information about the protected metadata’s validity, enabling iterative recovery of its values.
  • Attack vector: Network-accessible with no authentication and no user interaction required (AV:N/AC:L/PR:N/UI:N). The RadAsyncUpload handler is exposed over standard HTTP/HTTPS on ASP.NET applications hosted on IIS.
  • Impact: High confidentiality impact — an attacker can recover cryptographically protected upload metadata. Recovery of RadAsyncUpload metadata values is a known precursor to more severe exploitation: previous vulnerabilities in the same component demonstrated that weaknesses in its cryptographic metadata handling could be leveraged for deserialization-based remote code execution.

Affected software

  • Progress Telerik UI for ASP.NET AJAX versions 2010.1.309 through 2026.2.707 (all versions prior to v2026.2.708)

Severity

  • CVSS v3.1 Base Score: 7.5 (High)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Mitigation and recommended actions

  • Immediate: Upgrade to Progress Telerik UI for ASP.NET AJAX version 2026.2.708 (2026 Q2 SP1) or later. This release introduces AES-GCM encryption to address the timing oracle in metadata processing.
  • If immediate upgrade is not feasible:
    • If RadAsyncUpload is not required by the application, disable its HTTP handler entirely by setting Telerik.Web.DisableAsyncUploadHandler to true in web.config.
    • For deployments using custom encryption keys, remove custom key configurations from web.config to revert metadata protection to MachineKey.Unprotect (AES + HMAC), and configure strong, non-auto-generated machine keys via IIS Manager (set validation to HMACSHA256, disable "automatically generate at runtime", and recycle the application pool after applying keys).

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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