CVE-2026-58649Important
.NET Information Disclosure Vulnerability
Assessment
Origin validation error in .NET allows an unauthorized attacker to disclose information over a network.
- Severity
- Important
- CVSS base score
- 6.5CVSS:3.1/
AV:N/ AC:L/ PR:N/ UI:R/ S:U/ C:H/ I:N/ A:N/ E:U/ RL:O/ RC:C - Impact
- Information Disclosure
- EPSS, next 30 days
- 0.3%Higher than 17.6% of scored CVEs · FIRST model run 26 Sep 2026 · about EPSS
- Exploitability
- Exploitation Less Likely
- Publicly disclosed
- No
- Customer action
- Required: apply the update
- Component
- .NET
- Weakness
- CWE-346: Origin Validation Error
- Issued by
- Microsoft
- Published
- 8 Sep 2026 · September 2026
- Last revised
- 8 Sep 2026
Updates that fix it
3 KBs| KB | Type | Restart | Applies to | Other CVEs |
|---|---|---|---|---|
| KB5126104 | Security Update | Required | .NET 8.0 installed on Linux, .NET 8.0 installed on Mac OS, .NET 8.0 installed on Windows | All CVEs in KB5126104 |
| KB5126105 | Security Update | Required | .NET 9.0 installed on Linux, .NET 9.0 installed on Mac OS, .NET 9.0 installed on Windows | All CVEs in KB5126105 |
| KB5126106 | Security Update | Required | .NET 10.0 installed on Linux, .NET 10.0 installed on Mac OS, .NET 10.0 installed on Windows | All CVEs in KB5126106 |
Affected products
Developer Tools14 affected products
- .NET 10.0 installed on Linux
- .NET 10.0 installed on Mac OS
- .NET 10.0 installed on Windows
- .NET 11.0 installed on Linux
- .NET 11.0 installed on Mac OS
- .NET 11.0 installed on Windows
- .NET 8.0 installed on Linux
- .NET 8.0 installed on Mac OS
- .NET 8.0 installed on Windows
- .NET 9.0 installed on Linux
- .NET 9.0 installed on Mac OS
- .NET 9.0 installed on Windows
- Microsoft Visual Studio 2022 version 17.14
- Microsoft Visual Studio 2026 version 18.9