Security Digest · Vulnerability record
CVE-2026-26030: Microsoft Semantic Kernel InMemoryVectorStore filter functionality vulnerable to remote code execution
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.
CVSS 10.0 Critical EPSS 4.1% · p91
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 4.1%, percentile 91: FIRST’s model estimates a 4.1% chance of exploitation activity in the next 30 days, higher than 91% 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) < 1.39.4, fixed in 1.39.4. Check your lockfile, including transitive dependencies.
What it is
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.
From the GitHub advisory
Impact: An RCE vulnerability has been identified in Microsoft Semantic Kernel Python SDK, specifically within the InMemoryVectorStore filter functionality.
Patches: The problem has been fixed in python-1.39.4. Users should upgrade this version or higher.
Workarounds: Avoid using InMemoryVectorStore for production scenarios.
References: Release python-1.39.4 · microsoft/semantic-kernel · GitHub PR to block use of dangerous attribute names that must not be accessed in filter expressions
Weakness type: CWE-94.
Product: semantic-kernel (PyPI) · Assigned by: GitHub_M · Published: 2026-02-19
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| PyPI | semantic-kernel | < 1.39.4 | 1.39.4 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| microsoft | semantic-kernel | < 1.39.4 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_M | 3.1 | 10 Critical | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H |
| GitHub | 3.1 | 9.9 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H |
- 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): 4.13% probability of exploitation activity in the next 30 days; percentile 91.
Timeline
- — CVE record published by GitHub_M
- — GitHub-reviewed advisory GHSA-xjw9-4gw8-4rqx published (critical)
- — 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
- GitHub Advisory GHSA-xjw9-4gw8-4rqx github.com
- CVE.org record CVE-2026-26030 cve.org
- NVD entry CVE-2026-26030 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- github.com github.com
- github.com github.com
- github.com github.com