CriticalCVE-2017-11317

    Telerik UI for ASP.NET AJAX Unrestricted File Upload Vulnerability (CVE-2017-11317)

    Published In CISA KEV since Sources: CVE.org

    What is affected, what to do

    Telerik.Web.UI in Progress Telerik UI for ASP.NET AJAX before R1 2017 and R2 before R2 2017 SP2 uses weak RadAsyncUpload encryption, which allows remote attackers to perform arbitrary file uploads or execute arbitrary code.

    The vulnerability is being actively exploited; treat it as a priority. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Progress Telerik UI for ASP.NET AJAX lte *..2016.3.1027
    • Progress Telerik UI for ASP.NET AJAX eq 2017.2.503..2017.2.503
    • Progress Telerik UI for ASP.NET AJAX eq 2017.2.621..2017.2.621

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    9.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: CVE.org

    84.2 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.70

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    228.50 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

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    actively exploited
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

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    9.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.8
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

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    84.2 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    99.70
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 7 February 2025
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-326

    Response and mitigation

    Why act now?

    Prioritisation rationale

    The flaw is exploitable over the network with no authentication or user interaction, public exploit tooling has circulated for years, and its exploitation likelihood sits among the highest of any CVE. Attackers mass-scan for the WebResource.axd handler, then either drop webshells directly or chain this bug with CVE-2019-18935 to run code inside IIS; government agencies have been among the victims. Typical targets are internet-facing ASP.NET portals, CMS instances and business applications where Telerik is often embedded unnoticed as a third-party component. Treat any internet-reachable instance running a vulnerable build as critical and act immediately. Internal instances are high priority because they give an attacker easy lateral movement after initial access.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory: Sweep all IIS/ASP.NET applications for Telerik.Web.UI.dll and check the file version. Include third-party products that bundle Telerik, such as CMS platforms, portals and line-of-business apps. Affected are versions before R1 2017 and R2 releases before R2 2017 SP2; the context lists 2016.3.1027, 2017.2.503 and 2017.2.621.
      • Patch: Upgrade to at least R2 2017 SP2, and preferably straight to the current Telerik release. Older builds are also exposed to CVE-2019-18935, a deserialisation flaw frequently chained with this one. Look up the exact build number in the Progress vendor advisory. For bundled products, request the fixed release from the vendor.
      • Block the endpoint if you cannot patch now: At the reverse proxy or WAF, block internet requests to Telerik.Web.UI.WebResource.axd?type=rau unless the application genuinely needs RadAsyncUpload.
      • Set unique keys: Add strong, random values for Telerik.AsyncUpload.ConfigurationEncryptionKey, Telerik.Upload.ConfigurationHashKey and Telerik.Web.UI.DialogParametersEncryptionKey in web.config. Without them, the weak or publicly known default key remains in effect.
      • Compromise assessment: Hunt for new .aspx, .ashx, .asmx and .dll files in the webroot, App_Data/RadUploadTemp and C:\Windows\Temp. If you find any, isolate the host and preserve evidence.
      • Rotate secrets on suspicion: Replace the ASP.NET machineKey, the Telerik keys, database connection strings and any service-account passwords stored in web.config.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Keep internal Telerik apps off the internet. Place external ones in a DMZ and apply default-deny egress on the IIS host. This hampers reverse shells and tool staging.
      • WAF/IPS: Add a rule matching POST to Telerik.Web.UI.WebResource.axd with type=rau from untrusted sources. Also inspect the rauPostData multipart field and reject uploads ending in .aspx, .dll, .ashx or .config. Enable the available Suricata/ET signatures for "Telerik RadAsyncUpload".
      • Configuration: If RadAsyncUpload is unused, disable the handler. Newer builds support the Telerik.Web.DisableAsyncUploadHandler=true appSetting; otherwise, remove the handler mapping. Restrict upload types server-side via AllowedFileExtensions.
      • Endpoint hardening: Run the application pool under a dedicated low-privilege identity. Remove NTFS write rights on the webroot and deny execution in the temporary upload folder. Use AppLocker/WDAC to stop w3wp.exe loading unsigned DLLs from temp paths.
      • IAM / least privilege: Make sure web application service accounts hold no domain or local admin rights. Scope database accounts to the objects they actually need.

    3. Runbook step 3

      Detection rules

      • IIS access logs: Look for cs-method=POST with cs-uri-stem ending in Telerik.Web.UI.WebResource.axd and cs-uri-query containing type=rau. Flag bursts from unfamiliar IPs or response sizes that deviate from baseline. Splunk: index=iis cs_uri_stem="*Telerik.Web.UI.WebResource.axd" cs_uri_query="*type=rau*" cs_method=POST | stats count by c_ip
      • Sysmon EID 1 / EDR process ancestry: Alert when w3wp.exe spawns cmd.exe, powershell.exe, whoami.exe, certutil.exe or rundll32.exe. KQL: DeviceProcessEvents | where InitiatingProcessFileName =~ "w3wp.exe" and FileName in~ ("cmd.exe","powershell.exe","whoami.exe","certutil.exe")
      • Sysmon EID 11 (FileCreate): Alert when w3wp.exe writes .aspx, .ashx or .dll files into the webroot, RadUploadTemp or C:\Windows\Temp. This is the classic webshell and payload drop pattern.
      • Sysmon EID 7 (ImageLoad): Alert when w3wp.exe loads a DLL from C:\Windows\Temp\ or an upload directory. This is the hallmark of the CVE-2019-18935 chain. Sigma shape: Image|endswith: '\w3wp.exe' and ImageLoaded|contains: '\Windows\Temp\'
      • Windows Application log: Watch for ASP.NET error events (Event ID 1309) referencing Telerik.Web.UI or decryption and deserialisation failures. These spike during scanning and exploit attempts.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    Telerik.Web.UI in Progress Telerik UI for ASP.NET AJAX before R1 2017 and R2 before R2 2017 SP2 uses weak RadAsyncUpload encryption, which allows remote attackers to perform arbitrary file uploads or execute arbitrary code.

    Source: NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    telerikui_for_asp.net_ajax
    • 2017.2.503
    • 2017.2.621
    • ≤ 2016.3.1027
    • —
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-326Inadequate Encryption Strength

      Class

      The product stores or transmits sensitive data using an encryption scheme that is theoretically sound, but is not strong enough for the level of protection required.

      Entry at MITRE CWE-326

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    Packet StormTelerik UI ASP.NET AJAX RadAsyncUpload Deserialization (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Exploit-DBEDB-ID 43874 (opens in a new tab)exploit-db.comPoC (publicly reported)reported, not verified—

    References & sources

    • exploit-db.com43874Exploit, x_refsource_EXPLOIT-DB, Exploit, Third-party advisory, Vulnerability database
    • telerik.comsupport/kb/aspnet-ajax/upload-(async)/details/unrestricted-file…x_refsource_CONFIRM, Mitigation, Vendor advisory
    • psirt.global.sonicwall.comvuln-detail/SNWLID-2018-0006x_refsource_CONFIRM, Third-party advisory
    • packetstormsecurity.comfiles/159653/Telerik-UI-ASP.NET-AJAX-RadAsyncUpload-Deserializa…x_refsource_MISC, Exploit, Third-party advisory, Vulnerability database
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2017-11317government-resource, US government resource
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