CVE-2026-26030: Semantic Kernel Python SDK RCE Vulnerability

CVE-2026-26030 Overview

CVE-2026-26030 is a critical remote code execution (RCE) vulnerability affecting Microsoft's Semantic Kernel Python SDK. The vulnerability exists within the InMemoryVectorStore filter functionality in versions prior to 1.39.4. This code injection flaw (CWE-94) allows authenticated attackers to execute arbitrary code remotely, potentially leading to complete system compromise.

Semantic Kernel is Microsoft's open-source SDK that enables developers to integrate large language models (LLMs) into their applications. The vulnerable InMemoryVectorStore component is commonly used for vector-based data storage and retrieval operations in AI/ML applications.

Critical Impact

This vulnerability enables remote code execution through the InMemoryVectorStore filter functionality, allowing attackers with low privileges to execute arbitrary code on affected systems with potential cross-scope impact on confidentiality, integrity, and availability.

Affected Products

• Microsoft Semantic Kernel Python SDK versions prior to 1.39.4
• Applications utilizing InMemoryVectorStore filter functionality
• AI/ML applications built on vulnerable Semantic Kernel versions

Discovery Timeline

• 2026-02-19 - CVE-2026-26030 published to NVD
• 2026-02-19 - Last updated in NVD database

Technical Details for CVE-2026-26030

Vulnerability Analysis

This vulnerability is classified as Code Injection (CWE-94), occurring within the InMemoryVectorStore filter functionality of the Semantic Kernel Python SDK. The flaw allows attackers to inject and execute arbitrary code through maliciously crafted filter parameters processed by the vector store component.

The vulnerability is network-accessible and requires low attack complexity, making it relatively straightforward to exploit. While authentication is required (low privileges), the scope is changed, meaning a successful exploit can impact resources beyond the vulnerable component's security scope. This characteristic makes the vulnerability particularly dangerous in multi-tenant or containerized environments where lateral movement could occur.

Root Cause

The root cause of CVE-2026-26030 lies in improper input validation and sanitization within the InMemoryVectorStore filter processing logic. The filter functionality fails to adequately validate user-supplied input before processing, allowing malicious code to be injected and subsequently executed within the application context. This code injection vulnerability enables attackers to bypass intended security controls and execute arbitrary Python code.

Attack Vector

The attack vector for this vulnerability is network-based, requiring no user interaction. An attacker with low-level authentication to an application using the vulnerable Semantic Kernel SDK can craft malicious filter parameters targeting the InMemoryVectorStore component. When the application processes these malicious filters, the injected code executes with the privileges of the application, potentially leading to:

• Complete compromise of the affected application
• Data exfiltration from vector stores and connected data sources
• Lateral movement to other systems accessible by the compromised application
• Persistence mechanisms establishment within the environment

The vulnerability manifests in the filter processing mechanism of InMemoryVectorStore. When filter parameters are passed to the vector store for data retrieval operations, insufficient sanitization allows code injection. For detailed technical analysis, see the GitHub Security Advisory and the associated pull request that addresses the vulnerability.

Detection Methods for CVE-2026-26030

Indicators of Compromise

• Unusual or malformed filter parameters in application logs targeting InMemoryVectorStore operations
• Unexpected process spawning or network connections originating from Python applications using Semantic Kernel
• Anomalous code execution patterns or system calls from applications leveraging the SDK
• Suspicious error messages related to filter parsing or vector store operations

Detection Strategies

• Monitor application logs for unusual InMemoryVectorStore filter operations containing suspicious patterns or code-like strings
• Implement runtime application self-protection (RASP) to detect code injection attempts in real-time
• Deploy network monitoring to identify unexpected outbound connections from applications using Semantic Kernel
• Utilize SentinelOne's Singularity Platform to detect anomalous process behavior and code execution patterns associated with exploitation attempts

Monitoring Recommendations

• Enable verbose logging for Semantic Kernel SDK operations, particularly around InMemoryVectorStore filter processing
• Implement alerting for failed or malformed filter operations that could indicate reconnaissance or exploitation attempts
• Monitor for privilege escalation attempts or unauthorized resource access following vector store operations
• Review application dependencies regularly to identify outdated Semantic Kernel SDK versions

How to Mitigate CVE-2026-26030

Immediate Actions Required

• Upgrade Microsoft Semantic Kernel Python SDK to version 1.39.4 or higher immediately
• Audit all applications using Semantic Kernel to identify instances of InMemoryVectorStore usage
• If immediate patching is not possible, disable or avoid using InMemoryVectorStore in production environments
• Review application logs for any historical indicators of exploitation attempts

Patch Information

Microsoft has released version python-1.39.4 of the Semantic Kernel SDK to address this vulnerability. The fix is available through the official GitHub release. Organizations should update their dependencies using pip:

# Upgrade Semantic Kernel to patched version
pip install --upgrade semantic-kernel>=1.39.4

# Verify installed version
pip show semantic-kernel | grep Version

The patch addresses the code injection vulnerability by implementing proper input validation and sanitization for filter parameters in the InMemoryVectorStore component. Technical details of the fix can be reviewed in the GitHub Pull Request #13505.

Workarounds

• Avoid using InMemoryVectorStore for production scenarios until the patch can be applied
• Implement strict input validation at the application layer before passing filter parameters to Semantic Kernel
• Deploy network segmentation to limit the blast radius of potential exploitation
• Use alternative vector store implementations that are not affected by this vulnerability

# Configuration example - Verify Semantic Kernel version
pip freeze | grep semantic-kernel
# Expected output: semantic-kernel>=1.39.4

# Alternative: Pin to safe version in requirements.txt
echo "semantic-kernel>=1.39.4" >> requirements.txt
pip install -r requirements.txt