🛡️ CVE-2026-62899 — .net
Description
Microsoft Security Advisory CVE-2026-62899 – .NET Security Feature Bypass Vulnerability
Executive summary
Microsoft is releasing this security advisory to provide information about a vulnerability in System.Net.HttpListener. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.
Inconsistent interpretation of http requests ('http request/response smuggling') in .NET allows an unauthorized attacker to bypass a security feature over a network.
Announcement
Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/427
CVSS Details
- Version: 3.1
- Severity: Medium
- Score: 5.9
- Vector:
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C - Weakness: CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Affected Platforms
- Platforms: Linux, macOS
- Architectures: All
<a name="affected-packages"></a>Affected Packages
The vulnerability affects any Microsoft .NET project if it uses any of affected package versions listed below
<a name=".NET 10"></a>.NET 10
Package name | Affected version | Patched version
------------ | ---------------- | -------------------------
[Microsoft.NETCore.App.Runtime.linux-arm](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-arm) | >= 10.0.0, <= 10.0.10 | 10.0.11
[Microsoft.NETCore.App.Runtime.linux-arm64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-arm64) | >= 10.0.0, <= 10.0.10 | 10.0.11
[Microsoft.NETCore.App.Runtime.linux-musl-arm](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-musl-arm) | >= 10.0.0, <= 10.0.10 | 10.0.11
[Microsoft.NETCore.App.Runtime.linux-musl-arm64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-musl-arm64) | >= 10.0.0, <= 10.0.10 | 10.0.11
[Microsoft.NETCore.App.Runtime.linux-musl-x64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-musl-x64) | >= 10.0.0, <= 10.0.10 | 10.0.11
[Microsoft.NETCore.App.Runtime.linux-x64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-x64) | >= 10.0.0, <= 10.0.10 | 10.0.11
[Microsoft.NETCore.App.Runtime.osx-arm64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.osx-arm64) | >= 10.0.0, <= 10.0.10 | 10.0.11
[Microsoft.NETCore.App.Runtime.osx-x64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.osx-x64) | >= 10.0.0, <= 10.0.10 | 10.0.11
<a name=".NET 9"></a>.NET 9
Package name | Affected version | Patched version
------------ | ---------------- | -------------------------
[Microsoft.NETCore.App.Runtime.linux-arm](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-arm) | >= 9.0.0, <= 9.0.18 | 9.0.19
[Microsoft.NETCore.App.Runtime.linux-arm64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-arm64) | >= 9.0.0, <= 9.0.18 | 9.0.19
[Microsoft.NETCore.App.Runtime.linux-musl-arm](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-musl-arm) | >= 9.0.0, <= 9.0.18 | 9.0.19
[Microsoft.NETCore.App.Runtime.linux-musl-arm64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-musl-arm64) | >= 9.0.0, <= 9.0.18 | 9.0.19
[Microsoft.NETCore.App.Runtime.linux-musl-x64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-musl-x64) | >= 9.0.0, <= 9.0.18 | 9.0.19
[Microsoft.NETCore.App.Runtime.linux-x64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-x64) | >= 9.0.0, <= 9.0.18 | 9.0.19
[Microsoft.NETCore.App.Runtime.osx-arm64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.osx-arm64) | >= 9.0.0, <= 9.0.18 | 9.0.19
[Microsoft.NETCore.App.Runtime.osx-x64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.osx-x64) | >= 9.0.0, <= 9.0.18 | 9.0.19
<a name=".NET 8"></a>.NET 8
Package name | Affected version | Patched version
------------ | ---------------- | -------------------------
[Microsoft.NETCore.App.Runtime.linux-arm](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-arm) | >= 8.0.0, <= 8.0.29 | 8.0.30
[Microsoft.NETCore.App.Runtime.linux-arm64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-arm64) | >= 8.0.0, <= 8.0.29 | 8.0.30
[Microsoft.NETCore.App.Runtime.linux-musl-arm](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-musl-arm) | >= 8.0.0, <= 8.0.29 | 8.0.30
[Microsoft.NETCore.App.Runtime.linux-musl-arm64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-musl-arm64) | >= 8.0.0, <= 8.0.29 | 8.0.30
[Microsoft.NETCore.App.Runtime.linux-musl-x64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-musl-x64) | >= 8.0.0, <= 8.0.29 | 8.0.30
[Microsoft.NETCore.App.Runtime.linux-x64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.linux-x64) | >= 8.0.0, <= 8.0.29 | 8.0.30
[Microsoft.NETCore.App.Runtime.osx-arm64](https://www.nuget.org/packages/Microsoft.NETCore.App.Runtime.osx-arm64) |
How this vulnerability can be exploited
This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity none, availability none.
CVSS metrics in full
The score comes from this vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
- Attack vector: Network — reachable from anywhere that can route to the service.
- Attack complexity: High — the attacker first has to win a race, learn a secret or otherwise prepare the target.
- Privileges required: None — an unauthenticated stranger can try it.
- User interaction: None — nobody has to be tricked into anything.
- Scope: Unchanged — the damage stays inside the vulnerable component.
- Confidentiality impact: High — total loss, or loss the attacker controls.
- Integrity impact: None.
- Availability impact: None.
Weakness class
CVE-2026-62899 is classified as CWE-444: HTTP Request Smuggling. A proxy and a server disagree on where one request ends, letting an attacker slip a second request past the front end.
Affected software
CVE-2026-62899 is recorded against 13 packages.
- .net (from 10.0.0 up to 10.0.11)
- dotnet
- dotnet-sdk
- microsoft.netcore.app.runtime.linux-arm (from 8.0.0 up to 8.0.30)
- microsoft.netcore.app.runtime.linux-arm64 (from 8.0.0 up to 8.0.30)
- microsoft.netcore.app.runtime.linux-musl-arm (from 8.0.0 up to 8.0.30)
- microsoft.netcore.app.runtime.linux-musl-arm64 (from 8.0.0 up to 8.0.30)
- microsoft.netcore.app.runtime.linux-musl-x64 (from 8.0.0 up to 8.0.30)
- microsoft.netcore.app.runtime.linux-x64 (from 8.0.0 up to 8.0.30)
- microsoft.netcore.app.runtime.osx-arm64 (from 8.0.0 up to 8.0.30)
- microsoft.netcore.app.runtime.osx-x64 (from 8.0.0 up to 8.0.30)
- visual-studio-2022 (from 17.14.0 up to 17.14.38)
- visual-studio-2026 (from 18.8.0 up to 18.8.3)
Timeline and source
Published on 11 August 2026 and last revised on 14 August 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.
References
Other advisories for this package
.net has other advisories on record. If you are patching this one, these are worth checking on the same host:
- CVE-2026-62901 (7.5 High, published 11 Aug 2026)
- CVE-2026-62898 (7.5 High, published 11 Aug 2026)
- CVE-2026-62897 (7.0 High, published 11 Aug 2026)
- CVE-2026-70354 (7.8 High, published 11 Aug 2026)
- CVE-2026-62886 (7.8 High, published 11 Aug 2026)
- CVE-2026-62909 (7.8 High, published 11 Aug 2026)
- CVE-2026-62871 (7.8 High, published 11 Aug 2026)
- CVE-2026-62902 (6.5 Medium, published 11 Aug 2026)
Same weakness in other software
These advisories are the same class of weakness (CWE-444: HTTP Request Smuggling) in other software:
- CVE-2026-72587 (6.1 Medium, published 10 Aug 2026)
- CVE-2026-71554 (5.3 Medium, published 10 Aug 2026)
- CVE-2026-71324 (8.0 High, published 6 Aug 2026)
- CVE-2026-9190 (9.1 Critical, published 5 Aug 2026)
- CVE-2026-58044 (3.7 Low, published 4 Aug 2026)
- CVE-2026-16728 (4.8 Medium, published 3 Aug 2026)
- CVE-2026-69243 (published 3 Aug 2026)
- CVE-2026-58047 (published 31 Jul 2026)
Details
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Affected Packages
| Software | From version | Fixed in |
|---|---|---|
| .net | 10.0.0 | 10.0.11 |
| dotnet | — | — |
| dotnet-sdk | — | — |
| microsoft.netcore.app.runtime.linux-arm | 8.0.0 | 8.0.30 |
| microsoft.netcore.app.runtime.linux-arm64 | 8.0.0 | 8.0.30 |
| microsoft.netcore.app.runtime.linux-musl-arm | 8.0.0 | 8.0.30 |
| microsoft.netcore.app.runtime.linux-musl-arm64 | 8.0.0 | 8.0.30 |
| microsoft.netcore.app.runtime.linux-musl-x64 | 8.0.0 | 8.0.30 |
| microsoft.netcore.app.runtime.linux-x64 | 8.0.0 | 8.0.30 |
| microsoft.netcore.app.runtime.osx-arm64 | 8.0.0 | 8.0.30 |
| microsoft.netcore.app.runtime.osx-x64 | 8.0.0 | 8.0.30 |
| visual-studio-2022 | 17.14.0 | 17.14.38 |
| visual-studio-2026 | 18.8.0 | 18.8.3 |
References
Similar Threats
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