CVE-2026-13182 Overview
CVE-2026-13182 affects Progress Telerik UI for AJAX versions prior to v2026.2.708. The vulnerability resides in the RadAsyncUpload component, which processes encrypted client-state data during file upload operations. The component distinguishes between cryptographic decryption failures and invalid JSON parse failures through observable differences in error handling. This behavior creates an oracle that remote attackers can query to reveal protected metadata values. The flaw is categorized as an information disclosure issue tracked under [CWE-209: Generation of Error Message Containing Sensitive Information].
Critical Impact
Remote unauthenticated attackers can extract protected metadata from RadAsyncUpload client-state, exposing internal upload configuration values that were expected to remain confidential.
Affected Products
- Progress Telerik UI for AJAX prior to v2026.2.708
- Applications embedding the RadAsyncUpload control
- ASP.NET AJAX web applications using vulnerable Telerik assemblies
Discovery Timeline
- 2026-07-22 - CVE-2026-13182 published to NVD
- 2026-07-22 - Last updated in NVD database
Technical Details for CVE-2026-13182
Vulnerability Analysis
The RadAsyncUpload control accepts a client-state parameter containing encrypted metadata about the upload session. The server-side handler decrypts this payload and then parses the resulting plaintext as JSON. When the handler encounters a failure, it produces distinguishable responses depending on whether the failure originated in the cryptographic layer or the JSON parser. Attackers observe these differences to build a padding oracle. Repeated queries against the oracle let the attacker recover protected metadata values byte by byte without possessing the encryption key. The result is unauthorized disclosure of sensitive configuration values embedded in the client-state token.
Root Cause
The root cause is inconsistent error handling across the decrypt and parse stages of RadAsyncUpload client-state processing. The component returns discriminable signals for decryption failure versus invalid JSON, violating the principle that cryptographic operations must fail uniformly. This side channel enables classical padding oracle techniques against the underlying block cipher mode used to protect the client-state.
Attack Vector
Exploitation requires only network access to a vulnerable endpoint that exposes the RadAsyncUpload handler. The attacker submits crafted client-state values and observes response differences without authentication or user interaction. Refer to the Telerik Security Advisory CVE-2026-13182 for vendor-specific technical guidance. No public proof-of-concept exploit is documented in the NVD entry at the time of publication.
Detection Methods for CVE-2026-13182
Indicators of Compromise
- High-volume POST requests to Telerik.Web.UI.WebResource.axd or RadAsyncUpload handler endpoints from a single source.
- Repeated requests with slightly mutated rauPostData or client-state parameters, characteristic of oracle probing.
- Elevated rates of HTTP 500 or handler-specific error responses correlated with a single client IP.
Detection Strategies
- Inspect web server and WAF logs for iterative requests targeting RadAsyncUpload with malformed client-state tokens.
- Alert on anomalous ratios of upload-handler error responses compared to legitimate upload traffic baselines.
- Correlate application error telemetry that distinguishes decryption failures from JSON parse failures across short time windows.
Monitoring Recommendations
- Enable verbose logging on Telerik upload handlers and forward events to a centralized SIEM for correlation.
- Baseline normal RadAsyncUpload request volume per client and alert on statistical deviations.
- Monitor outbound egress from web tier hosts for signs of follow-on activity if metadata disclosure enables further attacks.
How to Mitigate CVE-2026-13182
Immediate Actions Required
- Upgrade Progress Telerik UI for AJAX to v2026.2.708 or later on all affected application servers.
- Inventory web applications for Telerik RadAsyncUpload usage, including transitive dependencies in third-party ASP.NET applications.
- Rotate any encryption keys and machine keys used by the vulnerable RadAsyncUpload configuration after patching.
Patch Information
Progress addresses CVE-2026-13182 in Telerik UI for AJAX v2026.2.708. The fix normalizes error handling so decryption failures and JSON parse failures become indistinguishable to remote observers. Consult the Telerik Security Advisory CVE-2026-13182 for the authoritative upgrade procedure and supported migration paths.
Workarounds
- Restrict access to RadAsyncUpload handler endpoints using network-level controls where the control is not required by end users.
- Deploy WAF rules that rate-limit and block iterative requests carrying malformed client-state tokens.
- Disable the RadAsyncUpload control in applications that do not rely on asynchronous upload functionality until patching completes.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
