GHSA-73j8-2gch-69rq BIT-dotnet-2026-26127 BIT-dotnet-sdk-2026-26127 CVE-2026-26127
.NET Denial of Service Vulnerability
- Severity
- 7.5 / 10
- High · CVSS 3.1
- Exploit chance (EPSS)
- 2.13%
- Chance of exploitation in the next 30 days. Higher than 81.98% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-125 Out-of-bounds Read
- Fix
- Available
- 13 packages have a fixed version
Description
Microsoft Security Advisory CVE-2026-26127 – .NET Denial of Service Vulnerability
Executive summary
Microsoft is releasing this security advisory to provide information about a vulnerability in .NET 9.0 and .NET 10.0. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.
A denial of service vulnerability exists in .NET and Microsoft.Bcl.Memory due to an out-of-bounds read when decoding malformed Base64Url input.
Announcement
Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/384
CVSS Details
- Version: 3.1
- Score: 7.5
- Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C - Severity: High
- Weakness: CWE-129 (Improper Validation of Array Index); CWE-125 (Out-of-bounds Read)
Affected Platforms
- Platforms: All
- Architectures: All
Affected Products
<a name=".NET 9"></a>.NET 9
| Package name | Affected version | Patched version |
|---|---|---|
| Microsoft.NetCore.App.Runtime.linux-arm | >= 9.0.0, <= 9.0.13 | 9.0.14 |
| Microsoft.NetCore.App.Runtime.linux-arm64 | >= 9.0.0, <= 9.0.13 | 9.0.14 |
| Microsoft.NetCore.App.Runtime.linux-musl-arm | >= 9.0.0, <= 9.0.13 | 9.0.14 |
| Microsoft.NetCore.App.Runtime.linux-musl-arm64 | >= 9.0.0, <= 9.0.13 | 9.0.14 |
| Microsoft.NetCore.App.Runtime.linux-musl-x64 | >= 9.0.0, <= 9.0.13 | 9.0.14 |
| Microsoft.NetCore.App.Runtime.linux-x64 | >= 9.0.0, <= 9.0.13 | 9.0.14 |
| Microsoft.NetCore.App.Runtime.osx-arm64 | >= 9.0.0, <= 9.0.13 | 9.0.14 |
| Microsoft.NetCore.App.Runtime.osx-x64 | >= 9.0.0, <= 9.0.13 | 9.0.14 |
| Microsoft.NetCore.App.Runtime.win-arm | >= 9.0.0, <= 9.0.13 | 9.0.14 |
| Microsoft.NetCore.App.Runtime.win-arm64 | >= 9.0.0, <= 9.0.13 | 9.0.14 |
| Microsoft.NetCore.App.Runtime.win-x64 | >= 9.0.0, <= 9.0.13 | 9.0.14 |
| Microsoft.NetCore.App.Runtime.win-x86 | >= 9.0.0, <= 9.0.13 | 9.0.14 |
<a name=".NET 10"></a>.NET 10
| Package name | Affected version | Patched version |
|---|---|---|
| Microsoft.NetCore.App.Runtime.linux-arm | >= 10.0.0, <= 10.0.3 | 10.0.4 |
| Microsoft.NetCore.App.Runtime.linux-arm64 | >= 10.0.0, <= 10.0.3 | 10.0.4 |
| Microsoft.NetCore.App.Runtime.linux-musl-arm | >= 10.0.0, <= 10.0.3 | 10.0.4 |
| Microsoft.NetCore.App.Runtime.linux-musl-arm64 | >= 10.0.0, <= 10.0.3 | 10.0.4 |
| Microsoft.NetCore.App.Runtime.linux-musl-x64 | >= 10.0.0, <= 10.0.3 | 10.0.4 |
| Microsoft.NetCore.App.Runtime.linux-x64 | >= 10.0.0, <= 10.0.3 | 10.0.4 |
| Microsoft.NetCore.App.Runtime.osx-arm64 | >= 10.0.0, <= 10.0.3 | 10.0.4 |
| Microsoft.NetCore.App.Runtime.osx-x64 | >= 10.0.0, <= 10.0.3 | 10.0.4 |
| Microsoft.NetCore.App.Runtime.win-arm | >= 10.0.0, <= 10.0.3 | 10.0.4 |
| Microsoft.NetCore.App.Runtime.win-arm64 | >= 10.0.0, <= 10.0.3 | 10.0.4 |
| Microsoft.NetCore.App.Runtime.win-x64 | >= 10.0.0, <= 10.0.3 | 10.0.4 |
| Microsoft.NetCore.App.Runtime.win-x86 | >= 10.0.0, <= 10.0.3 | 10.0.4 |
<a name="Microsoft.Bcl.Memory 9.0.14"></a>Microsoft.Bcl.Memory 9.0.14
| Package name | Affected version | Patched version |
|---|---|---|
| Microsoft.Bcl.Memory | >= 9.0.0, <= 9.0.13 | 9.0.14 |
<a name="Microsoft.Bcl.Memory 10.0.4"></a>Microsoft.Bcl.Memory 10.0.4
| Package name | Affected version | Patched version |
|---|---|---|
| Microsoft.Bcl.Memory | >= 10.0.0, <= 10.0.3 | 10.0.4 |
<a name="how-fix"></a>How to fix the issue
To update the Microsoft.Bcl.Memory NuGet package, apply one of the following methods:
NuGet Package Manager UI in Visual Studio:
- Open the project in Visual Studio.
- Right-click on the project in Solution Explorer and select "Manage NuGet Packages..." or navigate to "Project > Manage NuGet Packages".
- In the NuGet Package Manager window, select the "Updates" tab. This tab lists packages with available updates from the configured package sources.
- Select the package(s) to update. A specific version can be chosen from the dropdown, or the latest available version can be selected.
- Click the "Update" button.
Using the NuGet Package Manager Console in Visual Studio:
- Open the project in Visual Studio.
- Navigate to "Tools > NuGet Package Manager > Package Manager Console".
- To update a specific package to its latest version, run the following Update-Package command:
Update-Package -Id Microsoft.Bcl.Memory
Using the .NET CLI (Command Line Interface):
- Open a terminal or command prompt in the project's directory.
- To update a specific package to its latest version, run the following command:
dotnet package update Microsoft.Bcl.Memory
Once the NuGet package reference has been updated, the application must be recompiled and redeployed. Additionally, it is recommended to update the runtime and/or SDKs, but unless the application targets .NET 9 or higher, updating the runtime and/or SDK is not a required step to patch this vulnerability.
Other Information
Reporting Security Issues
If a potential security issue has been found in a supported version of .NET, it should be reported to the Microsoft Security Response Center (MSRC) via the MSRC Researcher Portal. Further information can be found in the MSRC Report an Issue FAQ.
Security reports made through MSRC may qualify for the Microsoft .NET Bounty. Details of the Microsoft .NET Bounty Program including terms and conditions are at https://aka.ms/corebounty.
Support
Questions about this issue can be asked on GitHub in the .NET GitHub organization. The main repos are located at https://github.com/dotnet/runtime. The Announcements repo (https://github.com/dotnet/Announcements) will contain this bulletin as an issue and will include a link to a discussion issue. Questions can be asked 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.
External Links
Revisions
V1.0 (March 10, 2026): Advisory published.
Affected versions
NuGet
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
Microsoft.Bcl.Memory NuGet → 9.0.14
- dotnet
dotnet add package Microsoft.Bcl.Memory --version 9.0.14
Microsoft.NetCore.App.Runtime.linux-arm NuGet → 9.0.14
- dotnet
dotnet add package Microsoft.NetCore.App.Runtime.linux-arm --version 9.0.14
Microsoft.NetCore.App.Runtime.linux-arm64 NuGet → 9.0.14
- dotnet
dotnet add package Microsoft.NetCore.App.Runtime.linux-arm64 --version 9.0.14
Microsoft.NetCore.App.Runtime.linux-musl-arm NuGet → 9.0.14
- dotnet
dotnet add package Microsoft.NetCore.App.Runtime.linux-musl-arm --version 9.0.14
Microsoft.NetCore.App.Runtime.linux-musl-arm64 NuGet → 9.0.14
- dotnet
dotnet add package Microsoft.NetCore.App.Runtime.linux-musl-arm64 --version 9.0.14
Microsoft.NetCore.App.Runtime.linux-musl-x64 NuGet → 9.0.14
- dotnet
dotnet add package Microsoft.NetCore.App.Runtime.linux-musl-x64 --version 9.0.14
Microsoft.NetCore.App.Runtime.linux-x64 NuGet → 9.0.14
- dotnet
dotnet add package Microsoft.NetCore.App.Runtime.linux-x64 --version 9.0.14
Microsoft.NetCore.App.Runtime.osx-arm64 NuGet → 9.0.14
- dotnet
dotnet add package Microsoft.NetCore.App.Runtime.osx-arm64 --version 9.0.14
Microsoft.NetCore.App.Runtime.osx-x64 NuGet → 9.0.14
- dotnet
dotnet add package Microsoft.NetCore.App.Runtime.osx-x64 --version 9.0.14
Microsoft.NetCore.App.Runtime.win-arm NuGet → 9.0.14
- dotnet
dotnet add package Microsoft.NetCore.App.Runtime.win-arm --version 9.0.14
Microsoft.NetCore.App.Runtime.win-arm64 NuGet → 9.0.14
- dotnet
dotnet add package Microsoft.NetCore.App.Runtime.win-arm64 --version 9.0.14
Microsoft.NetCore.App.Runtime.win-x64 NuGet → 9.0.14
- dotnet
dotnet add package Microsoft.NetCore.App.Runtime.win-x64 --version 9.0.14
Microsoft.NetCore.App.Runtime.win-x86 NuGet → 9.0.14
- dotnet
dotnet add package Microsoft.NetCore.App.Runtime.win-x86 --version 9.0.14
Severity breakdown
CVSS 3.1 7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Weakness
CWE-125: Out-of-bounds Read
The product reads data past the end, or before the beginning, of the intended buffer.
How to prevent it
- Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright. To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.
- Architecture and Design: Use a language that provides appropriate memory abstractions.
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| CVE-2020-1147 .NET Framework, SharePoint Server, and Visual Studio Remote Code Execution Vulnerability | High Known exploited | Also affects Microsoft.NETCore.App.Runtime.linux-arm |
| GHSA-87vj-4hqv-22p9 Microsoft Security Advisory CVE-2026-96233 - .NET and Visual Studio Denial of Service Vulnerability | High | Also affects Microsoft.NETCore.App.Runtime.linux-arm |
| GHSA-2j93-m82w-73j2 Microsoft Security Advisory CVE-2026-96231 - .NET and Visual Studio Elevation of Privilege Vulnerability | High | Also affects Microsoft.NETCore.App.Runtime.linux-arm |
| GHSA-w6wh-p4g7-mpj2 Microsoft Security Advisory CVE-2026-96225 - .NET and Visual Studio Elevation of Privilege Vulnerability | High | Also affects Microsoft.NETCore.App.Runtime.linux-arm |
| GHSA-4mpw-cpwj-hxxj Microsoft Security Advisory CVE-2026-70197 - .NET and Visual Studio Remote Code Execution Vulnerability | High | Also affects Microsoft.NETCore.App.Runtime.win-arm64 |
| GHSA-fqpq-cx42-9jmm Microsoft Security Advisory CVE-2026-70194 - .NET and Visual Studio Security Feature Bypass Vulnerability | Medium | Also affects Microsoft.NETCore.App.Runtime.linux-arm |
| GHSA-3rxq-g8rj-r2cf Microsoft Security Advisory CVE-2026-69651 - .NET and Visual Studio Denial of Service Vulnerability | High | Also affects Microsoft.NETCore.App.Runtime.linux-arm |
| GHSA-wxxw-5cvc-53j7 Microsoft Security Advisory CVE-2026-66822 - .NET and Visual Studio Information Disclosure Vulnerability | Medium | Also affects Microsoft.NETCore.App.Runtime.linux-arm |
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