Microsoft has announced that it has fixed six vulnerabilities, including CVE-2026-85889 with a maximum CVSS score of 10.0 in the Azure AI Foundry platform. According to the company, the vulnerability allowed an unauthenticated attacker to escalate privileges over the network due to missing authentication in a critical function. Microsoft states that the four cloud vulnerabilities have already been fully remediated on the service side and require no action from users. An out-of-band update KB5129194 has been released for two vulnerabilities in Windows 11 version 26H1.
Cloud vulnerabilities: details and status
The central vulnerability — CVE-2026-85889 — affects Azure AI Foundry (also known as Microsoft Foundry), an enterprise platform for building, deploying, and managing generative AI applications and agents. The vulnerability class is missing authentication for a critical function (Missing Authentication for Critical Function). Discovery is attributed to researcher Rémy Marot. According to Microsoft, no evidence of exploitation in real-world attacks has been found.
In addition to the main vulnerability, Microsoft reported fixing three more critical cloud bugs:
- CVE-2026-85885 (CVSS 9.9) — command injection in Microsoft 365 Copilot, allowing an authenticated attacker to escalate privileges over the network
- CVE-2026-85878 (CVSS 9.9) — improper authorization in Azure Database for PostgreSQL with a similar privilege escalation vector
- CVE-2026-87701 (CVSS 9.6) — an improper neutralization vulnerability in Azure Cosmos DB, also leading to privilege escalation over the network
Important caveat: the CVSS scores and descriptions of these cloud vulnerabilities are based on information from a single source — Microsoft’s advisory. The MSRC pages at the time of review did not display detailed content. None of the six vulnerabilities has been added to the CISA KEV catalog.
Windows vulnerabilities: update required
Unlike the cloud bugs, the two Windows vulnerabilities require specific action from administrators — installation of the out-of-band update:
- CVE-2026-62721 (CVSS 7.8) — insufficient access control granularity in Windows User-Mode Power Service (UMPS). An authenticated attacker can locally escalate privileges to SYSTEM level.
- CVE-2026-85921 (CVSS 8.2) — a double free memory error in Windows Secure Kernel Mode. It allows an authenticated attacker to locally obtain Virtual Trust Level 1 (VTL1) privileges — a level protected by virtualization technology.
Both vulnerabilities are fixed as part of the KB5129194 update dated September 14, 2026 for Windows 11 version 26H1 (build 28000.2956), available for x64 and arm64 architectures.
Difference in remediation models
The fundamental difference between the two groups of vulnerabilities lies in the remediation model. Microsoft fixes the cloud bugs (CVE-2026-85889, CVE-2026-85885, CVE-2026-85878, CVE-2026-87701) on the infrastructure side: customers do not need to install anything. This is standard practice for cloud CVEs — the company publishes an advisory for transparency, but the fix has already been applied. The Windows vulnerabilities (CVE-2026-62721 and CVE-2026-85921), by contrast, require administrators to install update KB5129194. These two bugs pose a practical risk for organizations that postpone patching.
We have previously covered actively exploited Windows vulnerabilities from Microsoft’s September patch cycle — in particular, the vulnerability in Windows ALPC and the vulnerability in Windows Update Stack. The current out-of-band release complements that large patch.
Recommendations
- For users of Azure cloud services and Microsoft 365 Copilot: no action is required — Microsoft states that the vulnerabilities have already been fixed on the platform side.
- For administrators of Windows 11 version 26H1: install update KB5129194 (build 28000.2956). CVE-2026-85921 with a score of 8.2 allows compromising the VTL1 virtualization level, which makes it a priority for systems using Virtualization-Based Security.
- Check your current OS build with the
winvercommand — the target build after the update is 28000.2956.
Although none of the six vulnerabilities is currently marked as exploited, the CVSS score of 10.0 for CVE-2026-85889 and 8.2 for CVE-2026-85921 indicate a high damage potential. Administrators of Windows 11 26H1 should install KB5129194 as soon as possible, paying particular attention to systems with Virtualization-Based Security enabled, where compromising VTL1 can undermine the entire isolation model.
