Microsoft.Build.Tasks.Core .NET Spoofing Vulnerability

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.0 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

EPSS

• CVE-2025-26646: 1.27% estimated exploitation activity in the next 30 days; percentile 69.78 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Microsoft Security Advisory CVE-2025-26646: .NET Spoofing Vulnerability <a name="executive-summary"</aExecutive summary Microsoft is releasing this security advisory to provide information about a vulnerability in .NET 9.0.xxx and .NET 8.0.xxx SDK. This advisory also provides guidance on what developers can do to update their applications to address this vulnerability. A vulnerability exists in .NET SDK or MSBuild applications where external control of file name or path allows an unauthorized attacked to perform spoofing over a network. Announcement Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/356 <a name="mitigation-factors"</aMitigation factors Projects which do not utilize the DownloadFile build task are not susceptible to this vulnerability. <a name="affected-software"</aAffected software Any installation of .NET 9.0.105 SDK, .NET 9.0.203 SDK or earlier. Any installation of .NET 8.0.115 SDK, .NET 8.0.311 or .NET 8.0.312 SDK, .NET…

Published by the source

13 May 2025, 21:38 UTC

Last modified by the source

16 Jun 2025, 13:54 UTC

Source last checked

26 Oct 2026, 17:03 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-h4j7-5rxr-p4wc

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# Patch Next advisory brief: CVE-2025-26646

Advisory: Microsoft.Build.Tasks.Core .NET Spoofing Vulnerability
IDs: CVE-2025-26646, GHSA-h4j7-5rxr-p4wc
Record: https://patchnext.com/advisories/cve-2025-26646 (revision 1, source checked 26 Oct 2026, 17:03 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: microsoft.build.tasks.core 17.14.8, 17.13.26, 17.12.36, 17.10.29, 17.8.29, 16.11.6, 15.9.30. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet microsoft.build.tasks.core: affected >= 15.8.166, <= 15.9.20; >= 16.0.461, <= 16.11.0; >= 17.0.0, <= 17.8.3; >= 17.9.5, <= 17.10.4; >= 17.11.4, <= 17.11.4; >= 17.12.6, <= 17.12.6; >= 17.13.9, <= 17.13.9; fixed in 17.8.29, 17.12.36, 17.14.8, 17.10.29, 15.9.30, 16.11.6, 17.13.26

## Suggested inspection (read-only)
- NuGet microsoft.build.tasks.core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on microsoft.build.tasks.core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-h4j7-5rxr-p4wc (GitHub-reviewed advisory GHSA-h4j7-5rxr-p4wc lists affected ranges: NuGet microsoft.build.tasks.core >=15.8.166 =16.0.461 =17.0.0 =17.9.5 =17.11.4 =17.12.6 =17.13.9 <=17.13.9)

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