Multiple threat actors exploited Progress Telerik bug to breach U.S. federal agency
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2019-18935 | Unauthenticated .NET Deserialization RCE in Progress Telerik UI for ASP.NET AJAX CVE-2019-18935 is a .NET deserialization flaw (CWE-502) in the RadAsyncUpload function of Progress Telerik UI for ASP.NET AJAX through version 2019.3.1023. It is triggered when an attacker who knows the Telerik upload encryption keys — most commonly because the earlier flaws CVE-2017-11317 or CVE-2017-11357 exposed them, though keys can be obtained by other means — sends crafted serialized data to RadAsyncUpload, allowing remote code execution without authentication. Successful exploitation gives an attacker arbitrary code execution on the hosting IIS/ASP.NET web server, reflected in the critical 9.8 CVSS score. Any web application built with Telerik UI for ASP.NET AJAX at or below 2019.3.1023 is affected, unless 2019.3.1023 has the non-default hardening setting enabled (as of 2020.1.114 a default setting prevents the exploit). Exploitation is rampant in the wild: the flaw was added to CISA KEV on 2021-11-03 with known ransomware use, carries a 99.7% EPSS probability of exploitation, has multiple public exploits (Bishop Fox, RAU_crypto, noperator), and has been used by multiple threat groups — including ransomware and government-linked actors — to breach organizations including a U.S. federal agency. Do: Upgrade to Progress Telerik UI for ASP.NET AJAX 2020.1.114 or later, where a default setting prevents exploitation (or, if staying on 2019.3.1023, enable the non-default hardening setting); per CISA KEV, apply updates per vendor instructions. Because exploitation requires the encryption keys to be known, also patch the older CVE-2017-11317/CVE-2017-11357 key-disclosure flaws or rotate the Telerik upload encryption keys. Check internet-facing IIS/ASP.NET applications for exposed RadAsyncUpload handlers and indicators of compromise, given known ransomware and federal-agency breaches. | 9.8 | 100% | KEV ransomware PoC ×4 |
| largeTens of thousands of internet-exposed ASP.NET/IIS web applications using Telerik controls (order-of-magnitude estimate) |
Indicators of compromiseauto-extracted · verify before use · export allAll →
| Type | Indicator | Context |
|---|---|---|
| domain | asp.net | zation vulnerability in Progress Telerik user interface for ASP.NET AJAX. Exploitation of this vulnerability allowed malicious |
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Multiple threat actors exploited a critical flaw in Progress Telerik to breach an unnamed US federal agency, said the US government.
A joint advisory issued by the Cybersecurity and Infrastructure Security Agency (CISA), Federal Bureau of Investigation (FBI), and Multi-State Information Sharing and Analysis Center (MS-ISAC) revealed that multiple threat actors, including a nation-state actor, exploited a critical vulnerability in Progress Telerik to breach an unnamed US federal agency.
The three-year-old vulnerability, tracked as CVE-2019-18935 (CVSS score: 9.8), is a .NET deserialization issue that resides in the Progress Telerik UI for ASP.NET AJAX. Exploitation can result in remote code execution.
“CISA analysts determined that multiple cyber threat actors, including an Advanced Persistent Threat (APT) actor, exploited a .NET deserialization vulnerability in Progress Telerik user interface for ASP.NET AJAX. Exploitation of this vulnerability allowed malicious actors to successfully execute remote code on a federal civilian executive branch (FCEB) agency’s Microsoft Internet Information Services (IIS) web server.” reads the advisory. “Actors were then able to upload malicious dynamic-link library (DLL) files (some masqueraded as portable network graphics [PNG] files) to the C:\Windows\Temp\ directory.”
Threat actors exploited the vulnerability to execute arbitrary code on a Microsoft Internet Information Services (IIS) web server used by a federal civilian executive branch (FCEB) agency.
In 2020 and 2021, this flaw was included by the US National Security Agency (NSA) in the list of the top 25 vulnerabilities exploited by Chinese state-sponsored hacking groups in attacks in the wild.
The flaw was also used in the past by the NetWalker ransomware gang in its operations.
The joint alert recommends network defenders review the Malware Analysis Report, MAR-10413062-1.v1 Telerik Vulnerability in U.S. Government IIS Server, to reference CISA’s analysis for the identified malicious files.
According to the MAR, CISA received 18 files for analysis from a forensic analysis engagement conducted at a Federal Civilian Executive Branch (FCEB) agency. Experts reported that 11 of the dynamic link library (DLL) files employed in the attack allows threat actors to read, create, and delete files on the target systems.
“If the DLL contains a hardcoded Internet Protocol (IP) address, status messages will be sent to the IP. One DLL file will attempt to collect the target system’s Transmission Control Protocol (TCP) connection table, and exfiltrate it to a remote Command and Control server (C2).” reads the MAR. “Five of the files drop and decode a reverse shell utility that can send and receive data and commands. In addition, the files drop and decode an Active Server Pages (ASPX) webshell. Two DLL files are capable of loading and executing payloads.”
US CISA has also provided Indicators of Compromise (IOCs) and YARA rules for detection in the Malware Analysis Report (MAR).
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