CVE-2026-26030 is a critical vulnerability classified under CWE-94 (Improper Control of Generation of Code), affecting Microsoft’s Semantic Kernel Python SDK, specifically versions prior to 1.39.4. The vulnerability resides in the InMemoryVectorStore filter functionality, which improperly controls code generation, enabling remote code execution (RCE). An attacker with low privileges (PR:L) can exploit this flaw remotely (AV:N) without requiring user interaction (UI:N), leading to complete compromise of confidentiality, integrity, and availability (C:H/I:H/A:H). The vulnerability’s scope is changed (S:C), meaning it can affect resources beyond the initially vulnerable component. The root cause is improper sanitization or validation of inputs that are used in dynamic code generation or execution within the InMemoryVectorStore filter, allowing malicious payloads to be injected and executed. Microsoft addressed this issue in version 1.39.4 of the Semantic Kernel SDK. Until upgrading, users should avoid using the vulnerable InMemoryVectorStore filter in production environments. No public exploits have been reported yet, but the critical severity and ease of exploitation make it a significant threat, especially for organizations leveraging Semantic Kernel for AI-driven applications or semantic data processing.

The impact of CVE-2026-26030 is severe, as it allows remote attackers to execute arbitrary code on affected systems, potentially leading to full system compromise. Confidential data handled by Semantic Kernel applications can be exposed or altered, undermining data integrity. Availability can be disrupted by malicious payloads causing denial of service or system crashes. Organizations relying on Semantic Kernel for AI or semantic processing may face operational disruptions, data breaches, or lateral movement within their networks. Given the vulnerability requires only low privileges and no user interaction, attackers can exploit it remotely with relative ease, increasing the risk of widespread attacks. The critical nature of this vulnerability demands immediate attention to prevent exploitation, especially in cloud environments, AI platforms, and services integrating Semantic Kernel components.

The primary mitigation is to upgrade Microsoft Semantic Kernel SDK to version 1.39.4 or later, where the vulnerability is fixed. Until upgrading is feasible, organizations should avoid using the InMemoryVectorStore filter functionality in production environments. Implement strict network segmentation and access controls to limit exposure of systems running vulnerable versions. Employ runtime application self-protection (RASP) or web application firewalls (WAF) with custom rules to detect and block suspicious inputs targeting code injection vectors. Conduct thorough code reviews and input validation audits on any custom extensions or integrations using Semantic Kernel. Monitor logs and network traffic for unusual activity indicative of exploitation attempts. Establish incident response plans specific to AI/semantic processing components to rapidly contain potential breaches. Finally, maintain up-to-date backups and test recovery procedures to mitigate impact from potential exploitation.