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CVE-2026-69439: CVE-2026-69439: Heap-based Buffer Overflow in Microsoft .NET and Visual Studio

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CVE-2026-69439: Heap-based Buffer Overflow in Microsoft .NET and Visual Studio

Vulnerability ID: CVE-2026-69439
CVSS Score: 8.8
Published: 2026-09-09

CVE-2026-69439 is a high-severity elevation of privilege vulnerability in Microsoft .NET and Visual Studio, originating from a heap-based buffer overflow (CWE-122) within native parsing libraries. An unauthenticated attacker can achieve code execution under the privileges of the active process by convincing a user to open a specially crafted project, metadata stream, or dependency.

TL;DR

An integer overflow in the native parsing components of .NET and Visual Studio allows network-based attackers to execute arbitrary code and elevate privileges when a user opens a maliciously crafted file.

Technical Details

  • Vulnerability Type: CWE-122: Heap-based Buffer Overflow
  • Attack Vector: Network (AV:N)
  • Attack Complexity: Low (AC:L)
  • Privileges Required: None (PR:N)
  • User Interaction: Required (UI:R)
  • Scope: Unchanged (S:U)
  • Impact Score: 5.9
  • Exploit Status: None (Unproven)

Affected Systems

  • Microsoft .NET Runtime and SDK environments
  • Microsoft Visual Studio 2022 development environment
  • Microsoft Visual Studio 2026 development environment
  • Hosts running custom applications using low-level .NET native integration
  • .NET 8.0: 8.0.0 to < 8.0.31 (Fixed in: 8.0.31)
  • .NET 9.0: 9.0.0 to < 9.0.20 (Fixed in: 9.0.20)
  • .NET 10.0: 10.0.0 to < 10.0.12 (Fixed in: 10.0.12)
  • .NET 11.0: 11.0.0 to < 11.0 RC1 (Fixed in: 11.0 RC1)
  • Visual Studio 2022: 17.14.0 to < 17.14.40 (Fixed in: 17.14.40)
  • Visual Studio 2026: 18.9.0 to < 18.9.3 (Fixed in: 18.9.3)

Mitigation Strategies

  • Apply official vendor patches immediately to development environments and runtime environments
  • Validate the integrity and source of imported solution files, templates, and NuGet packages
  • Utilize software restriction policies to limit the execution of unverified binaries
  • Enforce least privilege principles for developer accounts and execution contexts

Remediation Steps:

  1. Identify all installed .NET runtimes, SDKs, and Visual Studio instances
  2. Download and install security updates matching the architecture and version requirements
  3. Verify deployment by cross-checking active dll and runtime versions against the patched thresholds

References

Read the full report for CVE-2026-69439 on our website for more details including interactive diagrams and full exploit analysis.

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