Critical ASP.NET flaw hits QNAP NetBak PC Agent
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2025-55315 | HTTP Request Smuggling in Microsoft ASP.NET Core Enables Security Feature Bypass CVE-2025-55315 is an HTTP request/response smuggling vulnerability (CWE-444) in Microsoft ASP.NET Core, in which inconsistent interpretation of HTTP requests between the application and other HTTP-processing components can desynchronize request handling. An authorized (low-privileged) network attacker triggers it by sending crafted HTTP requests, and gains the ability to bypass a security feature; the scope-changed CVSS 9.9 score (C:H/I:H/A:L) indicates the bypass can affect resources beyond the vulnerable component with high confidentiality and integrity impact. All applications built on affected ASP.NET Core versions are in scope, Visual Studio 2022 is listed as an affected product, and related news coverage flags QNAP NetBak PC Agent as an impacted downstream product. No public proof-of-concept or CISA KEV listing exists, so exploitation is not confirmed in the wild, but the 65.8% EPSS (99th percentile) signals a high predicted likelihood of exploitation within 30 days. Microsoft addressed the flaw as part of its recent Patch Tuesday release covering 175 vulnerabilities. Do: Apply Microsoft's latest security updates for ASP.NET Core (runtime/SDK components) and Visual Studio 2022 immediately; exact patched version numbers are listed in Microsoft's advisory. QNAP NetBak PC Agent users should install the updated build referenced in QNAP's advisory. Given the 65.8% EPSS, prioritize internet-facing ASP.NET Core applications—especially those behind reverse proxies or load balancers where smuggling bypasses front-end security controls—and monitor for a public PoC or KEV listing. | 9.9 | 66% |
| mass≈ millions of installations (ASP.NET Core's default role in .NET web applications plus Visual Studio 2022's multi-million install base) |
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QNAP warns of critical ASP.NET flaw (CVE-2025-55315) in NetBak PC Agent, letting attackers hijack credentials or bypass security via HTTP smuggling.
QNAP urges users to patch a critical ASP.NET Core vulnerability, tracked as CVE-2025-55315 (CVSS score of 9.9), in its NetBak PC Agent for Windows. The flaw resides in the Kestrel server and lets low-privilege attackers hijack credentials or bypass front-end security via HTTP request smuggling.
“Inconsistent interpretation of http requests (‘http request/response smuggling’) in ASP.NET Core allows an authorized attacker to bypass a security feature over a network.” reads the advisory published by Microsoft. “An attacker who successfully exploited this vulnerability could smuggle another HTTP request and bypass front-end security controls or hijack other users’ credentials.”
Recently, Microsoft disclosed CVE-2025-55315 in ASP.NET Core, letting attackers bypass security via HTTP request smuggling, risking data access, file modification, or DoS.
“NetBak PC Agent installs and depends on Microsoft ASP.NET Core components during setup. Therefore, computers running NetBak PC Agent may contain an affected version of ASP.NET Core if the system has not been updated.” reads the advisory published by QNAP. “QNAP strongly recommends users ensure their Windows systems have the latest Microsoft ASP.NET Core updates installed.”
If exploited, an authenticated attacker can send crafted HTTP requests to access sensitive data, modify server files, or cause limited denial-of-service, the Taiwanese vendor states.
To address the issue, users can choose between two approaches. The first method involves reinstalling the NetBak PC Agent: uninstall the current version via Settings → Apps, then download and run the latest installer, which automatically updates the ASP.NET Core runtime components. The second method allows you to manually update ASP.NET Core by visiting the .NET 8.0 download page, installing the latest runtime hosting bundle (currently 8.0.21 as of October 2025), and then restarting your application or system.
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