critical CVSS 9.9 EPSS <0.1%

CVE-2026-26030·Python vulnerability

Semantic Kernel, Microsoft's semantic kernel Python SDK, has a remote code execution vulnerability in versions prior to 1.39.4, specifically within the `InMemoryVectorStore` filter functionality. The problem has been fixed in version `python-1.39.4`. Users should upgrade this version or higher. As a workaround, avoid using `InMemoryVectorStore` for production scenarios.

Severity
critical
Software
Python
Fixed in
1.39.4
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at <0.1% — higher than 25% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2026-26030 scores 9.9 on CVSS, so a successful attack would be serious — but at <0.1%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

Until: 1.39.4

Fixed in: 1.39.4

How to fix this CVE

Upgrade Microsoft's Semantic Kernel Python SDK to version 1.39.4 or later to patch a critical remote code execution flaw in the InMemoryVectorStore filter mechanism. This vulnerability allows authenticated attackers to execute arbitrary code on systems using affected versions. Immediately review your production deployments and apply the fix across all environments running Semantic Kernel.

sudo dnf update python3-semantic-kernel

Defensia detects this vulnerability

How to check if you are affected

  1. Check installed Semantic Kernel version: python3 -c "import semantic_kernel; print(semantic_kernel.__version__)"
  2. Verify if InMemoryVectorStore is imported in your application: grep -r "InMemoryVectorStore" /path/to/your/app/
  3. Search application logs for filter-related exceptions: grep -i "filter.*error\|vectorstore.*exception" /var/log/app/*.log
  4. Confirm the patch by re-running the version check after upgrade and verifying version is 1.39.4 or higher

FAQ

What is CVE-2026-26030?

A critical remote code execution vulnerability in Microsoft's Semantic Kernel Python SDK's InMemoryVectorStore filter functionality that allows authenticated users to execute arbitrary Python code on vulnerable systems.

Is CVE-2026-26030 being actively exploited?

No active exploitation has been reported by CISA, and no public exploit code is currently available. However, the high CVSS score (9.9) and ease of exploitation warrant immediate patching.

What versions of Python are affected by CVE-2026-26030?

All versions of the Semantic Kernel Python SDK prior to 1.39.4 are vulnerable. The exact earliest affected version is not specified, so assume all pre-1.39.4 installations require immediate remediation.

How do I check if my server is vulnerable to CVE-2026-26030?

Run: python3 -c "import semantic_kernel; print(semantic_kernel.__version__)" and compare the output to 1.39.4. If the version is lower, your system is vulnerable.

Does Defensia detect CVE-2026-26030?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Semantic Kernel Python SDK is installed on a monitored server, CVE-2026-26030 will appear in your dashboard with remediation steps.

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References

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