---
id: "CVE-2019-18935"
kind: "vulnerability"
aliases: ["CVE-2019-18935"]
title: "Progress Telerik UI for ASP.NET AJAX: Progress Telerik UI for ASP.NET AJAX Deserialization of Untrusted Data Vulnerability"
severity: "critical"
cvss: 9.8
epss: 0.99737
exploited: true
status: "open"
category: "package"
products: [{"name": "Progress Telerik UI for ASP.NET AJAX", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["asp.net", "exploited", "iis", "package", "ransomware", "telerik", "windows"]
not_affected_if: ["no-telerik-ui", "non-asp.net-stack"]
published_at: "2019-12-11T13:15:11+00:00"
first_seen_at: "2026-10-23T19:11:53+00:00"
updated_at: "2026-10-23T21:57:34+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2019-18935", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2019-18935", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2019-18935", "first_seen_at": "2026-10-23T21:57:34+00:00"}]
---

# Progress Telerik UI for ASP.NET AJAX: Progress Telerik UI for ASP.NET AJAX Deserialization of Untrusted Data Vulnerability

Progress Telerik UI for ASP.NET AJAX deserializes untrusted data through the RadAsyncUpload control, letting an unauthenticated request run code on the server. The attacker gets code execution as the w3wp.exe IIS worker process, and CISA lists it as actively exploited, including in ransomware campaigns.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Progress Telerik UI for ASP.NET AJAX affected ? fixed ?

## Fix

Apply the vendor update from Progress per the CISA required action; the fixed version is not stated in the sources.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2019-18935
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2019-18935
- 2026-10-23T21:57:34+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2019-18935

## From the sources

Progress Telerik UI for ASP.NET AJAX through 2019.3.1023 contains a .NET deserialization vulnerability in the RadAsyncUpload function. This is exploitable when the encryption keys are known due to the presence of CVE-2017-11317 or CVE-2017-11357, or other means. Exploitation can result in remote code execution. (As of 2020.1.114, a default setting prevents the exploit. In 2019.3.1023, but not earlier versions, a non-default setting can prevent exploitation.)

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_