Exploited CVEs / Progress / CVE-2019-18935

CVE-2019-18935

Progress Telerik UI for ASP.NET AJAX Deserialization of Untrusted Data Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted, and the vulnerability is known to be used in ransomware campaigns. Federal agencies were required to remediate by 2022-05-03 (that deadline has passed); treat that date as the outer bound for your own environment. The fix is in the vendor advisory: Progress Security Advisories, linked below.

Risk summary

CriticalCISA KEVRansomware

9.8

CVSS v3 base

100%

EPSS exploit probability

Critical

Severity

2021-11-03

Added to KEV

2022-05-03 (past due)

CISA due date

Actively exploited Progress Telerik UI for ASP.NET AJAX vulnerability, Critical severity, CVSS v3 9.8. Added to the CISA KEV catalog 2021-11-03.

Senserva AI read on CVE-2019-18935 CISA required action Official fix for CVE-2019-18935 Admin questions #79 hottest CVE right now

Senserva AI Opinion for CVE-2019-18935

Progress Telerik UI for ASP.NET AJAX deserializes untrusted data in its RadAsyncUpload handler, executing attacker code inside the w3wp.exe IIS worker process, and EPSS holds at the 100% maximum. The component is embedded invisibly in thousands of custom .NET web applications, so owners often do not know they run it; ransomware groups and state actors have both exploited it, including against a US federal agency per public advisories. Critical Severity and still being found in production apps today.

Do this: Search your IIS servers for Telerik.Web.UI.dll, record each version, and upgrade or remove every build older than the 2020 fixed releases.

AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2019-18935

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I run IT security. Facts for CVE-2019-18935, an actively exploited vulnerability (source: https://senserva.com/cve/CVE-2019-18935.html, data from CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2019-18935: Progress Telerik UI for ASP.NET AJAX Deserialization of Untrusted Data Vulnerability
- Affected: Progress Telerik UI for ASP.NET AJAX
- Severity: Critical, CVSS v3 9.8; EPSS 30-day exploitation probability 100%
- Added to CISA KEV: 2021-11-03; federal remediation due 2022-05-03
- Ransomware-linked: YES
- CISA required action: Apply updates per vendor instructions.
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) The fastest safe path to remediation. 4) How to check whether my environment is exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Patch immediately

Exploited in the wild and used in ransomware campaigns.

The fix ships from the vendor: Progress Security Advisories.

Do this now: Move this ahead of everything else in the queue, then verify the fix actually landed on every exposed device.

Updated August 29, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Full tracking and change history for CVE-2019-18935

Published: 2021-11-03
Last revised: 2021-11-03
Changes tracked: 1

Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.

Senserva Watchevery change we have recorded for this one

What changed, and when

2021-11-03 added to the CISA KEV catalog by CISA
2026-07-17 CVSS 0.0 to 9.8; EPSS first scored at 99.7%

Recorded by Senserva on the dates shown, from CISA KEV and FIRST EPSS. This is what moved and when, which neither the vendor advisory nor NVD publishes.

CISA required action

Federal (BOD 22-01) remediation due date: 2022-05-03 (past due).

Apply updates per vendor instructions.

Official fix for CVE-2019-18935

The authoritative fix and affected-version list are published by the vendor. Find the Telerik UI for ASP.NET AJAX advisory on Progress Security Advisories.

Progress Security Advisories CISA KEV entry

Common questions about CVE-2019-18935

Is CVE-2019-18935 actively exploited?

Yes. CVE-2019-18935 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2021-11-03, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 100%. CISA also reports it is known to be used in ransomware campaigns.

What is the CISA deadline and required action for CVE-2019-18935?

CISA set the federal (BOD 22-01) remediation due date at 2022-05-03, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply updates per vendor instructions.

What fixes CVE-2019-18935?

The authoritative fix is in the vendor advisory: see Progress Security Advisories for the patched Telerik UI for ASP.NET AJAX versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.

Can I ask my own AI about CVE-2019-18935?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2019-18935's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).

Scope and sources

More exploited Progress CVEs: CVE-2026-8037 CVE-2024-4885 CVE-2024-1212 CVE-2024-6670 CVE-2024-4358 CVE-2023-40044 CVE-2023-34362 CVE-2017-9248
All Progress exploited CVEs on one page: Progress vulnerabilities actively exploited.
Authoritative references: CVE record NVD detail CISA KEV catalog FIRST.org EPSS

Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.