CVE-2026-71328

Overview

.NET is a free, open-source, cross-platform framework for building modern apps and powerful cloud services. It consists of a runtime and a developer platform made up of tools, programming languages, and libraries for building many different types of applications.

A remote code execution vulnerability (CVE-2026-71328) has been identified in Microsoft.DiaSymReader.Native, the native symbol reader that the .NET shared framework carries on Windows. Microsoft states that the component can perform an out of bounds write while processing MSFZ format PDB files. HeroDevs investigation traced the .NET 6 exposure to the runtime's MicrosoftDiaSymReaderNativeVersion pin, which has sat inside the advisory's range since Microsoft's final .NET 6.0 release.

Per CWE-122: Heap-based Buffer Overflow, the weakness is a buffer overflow in which the buffer that is overwritten is allocated on the heap.

Every .NET 6 release up to and including NES for .NET 6.0.45 carries an affected version of the component. It ships in-box in the Microsoft.NETCore.App shared framework rather than as an opt-in package, and it is Windows-only, so Linux and macOS layouts do not carry it at all. Exploitation requires user interaction: something must read a crafted PDB. Microsoft also serviced supported releases in its September 8, 2026 security updates for .NET 8.0, .NET 9.0, and .NET 10.0. Additionally, if you've deployed self-contained applications targeting any of the impacted versions, these applications are also vulnerable and must be recompiled and redeployed.

Details

Module Info

• Product: .NET
• Affected packages: Microsoft.DiaSymReader.Native (in-box in the Microsoft.NETCore.App shared framework at runtimes/win/native/, not an opt-in package)
• Affected versions:
  
  • >=6.0.0 <=6.0.45
  • Microsoft.DiaSymReader.Native >=17.10.0-beta1.24272.1, <=18.9.0-beta1.26405.1
• Package manager: NuGet, Windows Installer, Docker
• GitHub repository: https://github.com/dotnet/runtime
• Published packages: Download .NET, Microsoft.DiaSymReader.Native on NuGet
• Fixed in:
  
  • NES for .NET 6.0.46

Vulnerability Info

This High-severity vulnerability is found in the native symbol reader carried by the Microsoft.NETCore.App shared framework on Windows, in versions of Microsoft.DiaSymReader.Native before 18.9.0-beta1.26405.2.

MSFZ is the newer compressed container format for Windows PDB data, which the reader parses through a different path from the classic MSF layout. Within that path, PSGSI1::readAddrMap reads the public symbol address map and sizes it from a count and an element width taken directly from the file. That arithmetic can wrap, and the wrapped value was then used to size the write, so a crafted MSFZ PDB declaring a count near the integer limit yields an allocation far smaller than the data written into it. Both the length and the contents are attacker-influenced.

This issue is specific to MSFZ symbol files, while CVE-2026-69439 and CVE-2026-69522 reach the classic Portable PDB and CodeView paths. All three were reported separately and are addressed together by the single Microsoft.DiaSymReader.Native package update in NES for .NET 6.0.46.

The advisory's lower bound, 17.10.0-beta1.24272.1, is the exact version Microsoft pinned in its own final .NET 6.0 release, so the weakness is present in every .NET 6 release from that point forward and likely earlier.

Mitigation

.NET 6 is End-of-Life and will not receive any updates to address this issue. For more information see .NET and .NET Core official support policy.

Users of the affected components should apply one of the following mitigations:

• Upgrade affected applications to one of: .NET Runtime >=8.0.31, .NET Runtime >=9.0.20, .NET Runtime >=10.0.12.
• Where an application references Microsoft.DiaSymReader.Native directly, update that reference to 18.9.0-beta1.26405.2 or later.
• Leverage a commercial support partner like HeroDevs for post-EOL security support, including NES for .NET 6.0.46 or later.