CVE-2026-62899Important
.NET Security Feature Bypass Vulnerability
Assessment
Inconsistent interpretation of http requests ('http request/response smuggling') in .NET allows an unauthorized attacker to bypass a security feature over a network.
- Severity
- Important
- CVSS base score
- 5.9CVSS:3.1/
AV:N/ AC:H/ PR:N/ UI:N/ S:U/ C:H/ I:N/ A:N/ E:U/ RL:O/ RC:C - Impact
- Security Feature Bypass
- EPSS, next 30 days
- 0.7%Higher than 53.1% 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-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
- Issued by
- Microsoft
- Published
- 11 Aug 2026 · August 2026
- Last revised
- 11 Aug 2026
Updates that fix it
3 KBs| KB | Type | Restart | Applies to | Other CVEs |
|---|---|---|---|---|
| KB5122104 | Security Update | — | .NET 8.0 installed on Linux, .NET 8.0 installed on Mac OS, .NET 8.0 installed on Windows | All CVEs in KB5122104 |
| KB5122105 | Security Update | — | .NET 9.0 installed on Linux, .NET 9.0 installed on Mac OS, .NET 9.0 installed on Windows | All CVEs in KB5122105 |
| KB5122106 | Security Update | — | .NET 10.0 installed on Linux, .NET 10.0 installed on Mac OS | All CVEs in KB5122106 |
Affected products
Developer Tools10 affected products
- .NET 10.0 installed on Linux
- .NET 10.0 installed on Mac OS
- .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 18.8