Skip to content

Microsoft.Build.Tasks.Core .NET Spoofing Vulnerability

Low severity GitHub Reviewed Published May 13, 2025 in dotnet/msbuild • Updated May 23, 2025

Package

nuget Microsoft.Build.Tasks.Core (NuGet)

Affected versions

>= 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
= 17.12.6
= 17.13.9

Patched versions

15.9.30
16.11.6
17.8.29
17.10.29
17.12.36
17.13.26
17.14.8

Description

Microsoft Security Advisory CVE-2025-26646: .NET Spoofing Vulnerability

Executive 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 dotnet/announcements#356

Mitigation factors

Projects which do not utilize the DownloadFile build task are not susceptible to this vulnerability.

Affected 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 8.0.408 or .NET 8.0.409 SDK or earlier.

Affected Packages

The vulnerability affects any Microsoft .NET Core project if it uses any of affected packages versions listed below

Package name Affected version Patched version
Microsoft.Build.Tasks.Core >= 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
17.12.6
17.13.9		 15.9.30
16.11.6
17.8.29
17.10.29
17.12.36
17.13.26
17.14.8

Advisory FAQ

How do I know if I am affected?

If you have a .NET SDK with a version listed, or an affected package listed in affected software or affected packages, you're exposed to the vulnerability.

How do I fix the issue?

  1. To fix the issue please install the latest version of .NET 9.0 SDK or .NET 8.0 SDK. If you have installed one or more .NET SDKs through Visual Studio, Visual Studio will prompt you to update Visual Studio, which will also update your .NET SDKs.
  2. If your application references the vulnerable package, update the package reference to the patched version.
  • You can list the versions you have installed by running the dotnet --info command. You will see output like the following;
.NET SDK:
 Version:           9.0.100
 Commit:            59db016f11
 Workload version:  9.0.100-manifests.3068a692
 MSBuild version:   17.12.7+5b8665660

Runtime Environment:
 OS Name:     Mac OS X
 OS Version:  15.2
 OS Platform: Darwin
 RID:         osx-arm64
 Base Path:   /usr/local/share/dotnet/sdk/9.0.100/

.NET workloads installed:
There are no installed workloads to display.
Configured to use loose manifests when installing new manifests.

Host:
  Version:      9.0.0
  Architecture: arm64
  Commit:       9d5a6a9aa4

.NET SDKs installed:
  9.0.100 [/usr/local/share/dotnet/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 9.0.0 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 9.0.0 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

Other architectures found:
  x64   [/usr/local/share/dotnet]
    registered at [/etc/dotnet/install_location_x64]

Environment variables:
  Not set

global.json file:
  Not found

Learn more:
  https://aka.ms/dotnet/info

Download .NET:
  https://aka.ms/dotnet/download

Once you have installed the updated SDK, restart your apps for the update to take effect.

Other Information

Reporting Security Issues

If you have found a potential security issue in .NET 8.0 or .NET 9.0, please email details to secure@microsoft.com. Reports may qualify for the Microsoft .NET Core & .NET 5 Bounty. Details of the Microsoft .NET Bounty Program including terms and conditions are at https://aka.ms/corebounty.

Support

You can ask questions about this issue on GitHub in the .NET GitHub organization. The main repos are located at https://github.com/dotnet/aspnetcore. The Announcements repo (https://github.com/dotnet/Announcements) will contain this bulletin as an issue and will include a link to a discussion issue. You can ask questions in the linked discussion issue.

Disclaimer

The information provided in this advisory is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

References

@rbhanda rbhanda published to dotnet/msbuild May 13, 2025
Published to the GitHub Advisory Database May 13, 2025
Reviewed May 13, 2025
Published by the National Vulnerability Database May 13, 2025
Last updated May 23, 2025

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality None
Integrity None
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(6th percentile)

Weaknesses

CVE ID

CVE-2025-26646

GHSA ID

GHSA-h4j7-5rxr-p4wc

Source code

Credits

Loading Checking history
See something to contribute? Suggest improvements for this vulnerability.