CVE-2026-25592: Semantic Kernel has Arbitrary File Write via AI Agent Function Calling in .NET SDK

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 2.4%, percentile 84: FIRST’s model estimates a 2.4% chance of exploitation activity in the next 30 days, higher than 84% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
• Needs an account (low (any account)). Exposure depends on who can log in.
• Only applies if your dependency tree includes semantic-kernel (PyPI) < 1.39.3, fixed in 1.39.3; Microsoft.SemanticKernel.Core (NuGet) < 1.71.0, fixed in 1.71.0. Check your lockfile, including transitive dependencies.

What it is

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.

From the GitHub advisory

Impact What kind of vulnerability is it? Who is impacted? An Arbitrary File Write vulnerability has been identified in Microsoft's Semantic Kernel .NET SDK, specifically within the SessionsPythonPlugin. Developers who have built applications which include Microsoft's Semantic Kernel .NET SDK and are using the SessionsPythonPlugin

Patches Has the problem been patched? What versions should users upgrade to? The problem has been fixed in Microsoft.SemanticKernel.Plugins.Core version 1.71.0. Users should upgrade to version 1.71.0 or higher.

Workarounds Is there a way for users to fix or remediate the vulnerability without upgrading? 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.

References Are there any links users can visit to find out more? - Sample showing safe use of the CodeInterpreterPlugin - PR to Add file upload security controls to SessionsPythonPlugin

Weakness type: CWE-22.

Product: semantic-kernel (PyPI) · Assigned by: GitHub_M · Published: 2026-02-06

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: low (any account)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 2.36% probability of exploitation activity in the next 30 days; percentile 84.

Timeline

• 2026-02-06 — CVE record published by GitHub_M
• 2026-02-06 — GitHub-reviewed advisory GHSA-2ww3-72rp-wpp4 published (critical)
• 2026-02-18 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-2ww3-72rp-wpp4 github.com
2. CVE.org record CVE-2026-25592 cve.org
3. NVD entry CVE-2026-25592 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com

Critical NuGet advisories · Today’s Security Digest