Microsoft · Semantic-Kernel · CVE-2026-25592
**Name of the Vulnerable Software and Affected Versions**
Microsoft Semantic Kernel .NET SDK versions prior to 1.71.0
Agent Framework version 1.0
**Description**
An arbitrary file write issue exists within the `SessionsPythonPlugin` of the .NET SDK. This flaw can be chained with path traversal and insecure automated optimizations to achieve remote code execution (RCE). The problem arises from a trust gap where stochastic LLM output is treated as high-privilege system commands when `AutoInvokeKernelFunctions` is enabled, failing to effectively validate tool calls. Attackers can bypass security filters using JSON type confusion, Base64/URL encoding, or Unicode homoglyphs to overwrite the application's own source code, such as `Program.cs`, leading to full host takeover. The issue specifically involves the `DownloadFileAsync()` and `UploadFileAsync()` functions and the `localFilePath` variable.
**Recommendations**
For Microsoft Semantic Kernel .NET SDK versions prior to 1.71.0, update to version 1.71.0 or higher.
For Agent Framework version 1.0, disable `ToolCallBehavior.AutoInvokeKernelFunctions` and switch to manual function invocation.
As a temporary mitigation, implement a Function Invocation Filter to verify that the `localFilePath` variable passed to `DownloadFileAsync()` or `UploadFileAsync()` is allow listed and anchored to a safe root.