CVE-2026-25592
CRITICALCVE-2026-25592 is a critical-severity (CVSS 9.9) Path Traversal vulnerability in Microsoft.SemanticKernel.Core. O3 Security confirms whether CVE-2026-25592 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Semantic Kernel has an Arbitrary File Write via AI Agent Function Calling in .NET SDK
Blast Radius
Microsoft.SemanticKernel.Core🐍semantic-kernelReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet, PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Semantic Kernel is an SDK used to build, orchestrate, and deploy AI agents and multi-agent systems. Prior to 1.71.0, an Arbitrary File Write vulnerability has been identified in Microsoft's Semantic Kernel .NET SDK, specifically within the SessionsPythonPlugin. The problem has been fixed in Microsoft.SemanticKernel.Core version 1.71.0. As a mitigation, users can create a Function Invocation Filter which checks the arguments being passed to any calls to DownloadFileAsync or UploadFileAsync and ensures the provided localFilePath is allow listed.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Microsoft.SemanticKernel.Core | all versions | 1.71.0 |
| 🐍PyPI | semantic-kernel | all versions | 1.39.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.SemanticKernel.Core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update Microsoft.SemanticKernel.Core to 1.71.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-25592 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-25592 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-25592. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-25592 in your dependencies?
O3 detects CVE-2026-25592 across NuGet, PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.