CVE-2026-50659
published 2026-07-14CVE-2026-50659: Improper encoding or escaping of output in .NET allows an authorized attacker to perform spoofing over a network.
PriorityP340medium6.5CVSS 3.1
AVNACLPRLUINSUCNIHAN
EPSS
0.55%
43.4th percentile
Improper encoding or escaping of output in .NET allows an authorized attacker to perform spoofing over a network.
Affected
65 ranges· showing 25
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| devspaces | udi-rhel9 | — | — |
| microsoft | microsoft.netcore.app.runtime.linux-arm | >= 10.0.0 < 10.0.10 | 10.0.10 |
| microsoft | microsoft.netcore.app.runtime.linux-arm | >= 8.0.0 < 8.0.29 | 8.0.29 |
| microsoft | microsoft.netcore.app.runtime.linux-arm | >= 9.0.0 < 9.0.18 | 9.0.18 |
| microsoft | microsoft.netcore.app.runtime.linux-arm64 | >= 10.0.0 < 10.0.10 | 10.0.10 |
| microsoft | microsoft.netcore.app.runtime.linux-arm64 | >= 8.0.0 < 8.0.29 | 8.0.29 |
| microsoft | microsoft.netcore.app.runtime.linux-arm64 | >= 9.0.0 < 9.0.18 | 9.0.18 |
| microsoft | microsoft.netcore.app.runtime.linux-musl-arm | >= 10.0.0 < 10.0.10 | 10.0.10 |
| microsoft | microsoft.netcore.app.runtime.linux-musl-arm | >= 8.0.0 < 8.0.29 | 8.0.29 |
| microsoft | microsoft.netcore.app.runtime.linux-musl-arm | >= 9.0.0 < 9.0.18 | 9.0.18 |
| microsoft | microsoft.netcore.app.runtime.linux-musl-arm64 | >= 10.0.0 < 10.0.10 | 10.0.10 |
| microsoft | microsoft.netcore.app.runtime.linux-musl-arm64 | >= 8.0.0 < 8.0.29 | 8.0.29 |
| microsoft | microsoft.netcore.app.runtime.linux-musl-arm64 | >= 9.0.0 < 9.0.18 | 9.0.18 |
| microsoft | microsoft.netcore.app.runtime.linux-musl-x64 | >= 10.0.0 < 10.0.10 | 10.0.10 |
| microsoft | microsoft.netcore.app.runtime.linux-musl-x64 | >= 8.0.0 < 8.0.29 | 8.0.29 |
| microsoft | microsoft.netcore.app.runtime.linux-musl-x64 | >= 9.0.0 < 9.0.18 | 9.0.18 |
| microsoft | microsoft.netcore.app.runtime.linux-x64 | >= 10.0.0 < 10.0.10 | 10.0.10 |
| microsoft | microsoft.netcore.app.runtime.linux-x64 | >= 8.0.0 < 8.0.29 | 8.0.29 |
| microsoft | microsoft.netcore.app.runtime.linux-x64 | >= 9.0.0 < 9.0.18 | 9.0.18 |
| microsoft | microsoft.netcore.app.runtime.osx-arm64 | >= 10.0.0 < 10.0.10 | 10.0.10 |
| microsoft | microsoft.netcore.app.runtime.osx-arm64 | >= 8.0.0 < 8.0.29 | 8.0.29 |
| microsoft | microsoft.netcore.app.runtime.osx-arm64 | >= 9.0.0 < 9.0.18 | 9.0.18 |
| microsoft | microsoft.netcore.app.runtime.osx-x64 | >= 10.0.0 < 10.0.10 | 10.0.10 |
| microsoft | microsoft.netcore.app.runtime.osx-x64 | >= 8.0.0 < 8.0.29 | 8.0.29 |
| microsoft | microsoft.netcore.app.runtime.osx-x64 | >= 9.0.0 < 9.0.18 | 9.0.18 |
CVSS provenance
nvdv3.16.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
ghsa6.5MEDIUM
vendor_ubuntu8.8HIGH
vendor_redhat6.5MEDIUM
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GHSA
Microsoft Security Advisory CVE-2026-50659 – .NET Spoofing Vulnerability
ghsa·2026-07-20·CVSS 6.5
CVE-2026-50659 [MEDIUM] CWE-116 Microsoft Security Advisory CVE-2026-50659 – .NET Spoofing Vulnerability
Microsoft Security Advisory CVE-2026-50659 – .NET Spoofing Vulnerability
## Executive summary
Microsoft is releasing this security advisory to provide information about a vulnerability in .NET SMTP client (System.Net.Mail). This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.
A spoofing vulnerability exists in the SMTP client implementation (System.Net.Mail) in .NET 8, .NET 9, and .NET 10, where an attacker can spoof messages during message routing.
## Announcement
Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/**TBD**
## CVSS Details
- **Version:** 3.1
- **Severity:** Medium
- **Score:** 6.5
- **Vector:** `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N`
- **Weakness:** CWE
VulDB
Microsoft NET Encoding encoding error
vuldb·2026-07-15·CVSS 6.5
CVE-2026-50659 [MEDIUM] Microsoft NET Encoding encoding error
A vulnerability classified as critical was found in Microsoft NET. The affected element is an unknown function of the component Encoding. The manipulation results in encoding error.
This vulnerability is identified as CVE-2026-50659. The attack can be executed remotely. There is not any exploit available.
Ubuntu
.NET vulnerabilities
vendor_ubuntu·2026-07-15·CVSS 8.8
CVE-2026-57108 [HIGH] .NET vulnerabilities
Title: .NET vulnerabilities
Summary: Several security issues were fixed in .NET.
Artur Stetsko discovered that the .NET did not properly validate
authentication data. An attacker could possibly use this issue to elevate
privileges. (CVE-2026-47300)
Levi Broderick discovered that .NET did not properly handle XML encryption
during parsing. An attacker could possibly use this issue to consume
excessive resources, resulting in a denial of service. (CVE-2026-47302)
Pham Quang Minh discovered that .NET did not properly parse
authentication data. An attacker could possibly use this issue to bypass
authentication and elevate privileges. (CVE-2026-47303)
Levi Broderick discovered that .NET did not properly verify cryptographic
signatures during XML encryption. An attacker could possibly use th
Red Hat
.NET: .NET: Network Spoofing Vulnerability
vendor_redhat·2026-07-14·CVSS 6.5
CVE-2026-50659 [MEDIUM] CWE-838 .NET: .NET: Network Spoofing Vulnerability
.NET: .NET: Network Spoofing Vulnerability
Improper encoding or escaping of output in .NET allows an authorized attacker to perform spoofing over a network.
A flaw was found in .NET. An authorized attacker can exploit this vulnerability by leveraging improper encoding or escaping of output. This allows the attacker to perform spoofing over a network, potentially deceiving users or systems into believing they are interacting with a trusted entity.
Package: devspaces/udi-rhel9 (Red Hat OpenShift Dev Spaces) - Affected
No detection rules found.
No public exploits indexed.
Rapid7
Patch Tuesday - July 2026
blogs_rapid7·2026-07-14·CVSS 9.6
CVE-2026-58617 [CRITICAL] Patch Tuesday - July 2026
Microsoft is publishing 622 vulnerabilities on July 2026 Patch Tuesday , including a record-breaking 416 Windows vulnerabilities. Microsoft is aware of exploitation in the wild for two of the vulnerabilities published today, both of which are listed on CISA KEV, as well as public disclosure for one other. As usual, browser vulns are not included in the Patch Tuesday count above. Rapid7 noted last month that Microsoft no longer enumerates Chromium CVEs in the Security Update Guide. However, Microsoft has now taken the pursuit of minimalism much further, since today’s Security Update Guide no longer lists out even Microsoft vulnerabilities! Instead, we now receive a summary table of vulnerability counts by product family, as well as a new slimline “Notable CVEs” section. All of this only ser
Sans Isc
Microsoft Patch Tuesday July 2026 - The AI Acopolypse is Here , (Tue, Jul 14th)
blogs_sans_isc·2026-07-14·CVSS 6.1
CVE-2026-56155 [MEDIUM] Microsoft Patch Tuesday July 2026 - The AI Acopolypse is Here , (Tue, Jul 14th)
Microsoft Patch Tuesday July 2026 - The AI Acopolypse is Here
Published: 2026-07-14. Last Updated: 2026-07-14 19:14:58 UTC
by Johannes Ullrich (Version: 1)
0 comment(s)
This patch Tuesday includes a staggering 622 vulnerabilities, not including another 427 vulnerabilities in Chromium, affecting Microsoft's Edge browser. 62 of the vulnerabilities are rated critical. One was disclosed before today, and two have already been exploited.
Given the large number of vulnerabilities, it is difficult to point out "noteworthy" issues.
Already exploited vulnerabilities:
CVE-2026-56155 : Active Directory Federation Services Elevation of Privilege Vulnerability. This is an important (not critical) vulnerablity.
CVE-2026-56164: Microsoft SharePoint Server Elevation of Privilege Vulnerability. Micr
Bugzilla
CVE-2026-50659 dotnet9.0: .NET: Network Spoofing Vulnerability [fedora-all]
bugzilla·2026-07-16·CVSS 6.5
CVE-2026-50659 [MEDIUM] CVE-2026-50659 dotnet9.0: .NET: Network Spoofing Vulnerability [fedora-all]
CVE-2026-50659 dotnet9.0: .NET: Network Spoofing Vulnerability [fedora-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
Improper encoding or escaping of output in .NET allows an authorized attacker to perform spoofing over a network.
Bugzilla
CVE-2026-50659 dotnet8.0: .NET: Network Spoofing Vulnerability [fedora-all]
bugzilla·2026-07-16·CVSS 6.5
CVE-2026-50659 [MEDIUM] CVE-2026-50659 dotnet8.0: .NET: Network Spoofing Vulnerability [fedora-all]
CVE-2026-50659 dotnet8.0: .NET: Network Spoofing Vulnerability [fedora-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
Improper encoding or escaping of output in .NET allows an authorized attacker to perform spoofing over a network.
Bugzilla
CVE-2026-50659 dotnet10.0: .NET: Network Spoofing Vulnerability [fedora-all]
bugzilla·2026-07-16·CVSS 6.5
CVE-2026-50659 [MEDIUM] CVE-2026-50659 dotnet10.0: .NET: Network Spoofing Vulnerability [fedora-all]
CVE-2026-50659 dotnet10.0: .NET: Network Spoofing Vulnerability [fedora-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
Improper encoding or escaping of output in .NET allows an authorized attacker to perform spoofing over a network.
Bugzilla
CVE-2026-50659 .NET: .NET: Network Spoofing Vulnerability
bugzilla·2026-07-14·CVSS 6.5
CVE-2026-50659 [MEDIUM] CVE-2026-50659 .NET: .NET: Network Spoofing Vulnerability
CVE-2026-50659 .NET: .NET: Network Spoofing Vulnerability
Improper encoding or escaping of output in .NET allows an authorized attacker to perform spoofing over a network.
Discussion:
This issue has been addressed in the following products:
Red Hat Enterprise Linux 8
Via RHSA-2026:41899 https://access.redhat.com/errata/RHSA-2026:41899
---
This issue has been addressed in the following products:
Red Hat Enterprise Linux 10
Via RHSA-2026:41893 https://access.redhat.com/errata/RHSA-2026:41893
---
This issue has been addressed in the following products:
Red Hat Enterprise Linux 10
Via RHSA-2026:41895 https://access.redhat.com/errata/RHSA-2026:41895
---
This issue has been addressed in the following products:
Red Hat Enterprise Linux 10
Via RHSA-2026:41897 https://access.redhat
2026-07-14
Published