CVE-2026-62899: .NET Security Feature Bypass Vulnerability

Overview

Severity
Medium (CVSS 5.9)
CVSS 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
Category
Security Feature Bypass
Exploit Status
Not Exploited
Exploitation Likelihood
Less Likely
Patch Tuesday
2026-Aug
Released
2026-08-11

Description

Inconsistent interpretation of http requests ('http request/response smuggling') in .NET allows an unauthorized attacker to bypass a security feature over a network.

FAQ

What kind of security feature could be bypassed by successfully exploiting this vulnerability? An attacker who successfully exploited this vulnerability could smuggle another HTTP request and bypass front-end security controls or hijack other users' credentials. According to the CVSS metric, the attack complexity is high (AC:H). What does that mean for this vulnerability? Successful exploitation of this vulnerability requires that the target system be set up in a specific manner and the attacker to have knowledge of that setup.

Affected Products (10)

Developer Tools

  • .NET 10.0 installed on Mac OS
  • .NET 10.0 installed on Linux
  • .NET 8.0 installed on Windows
  • .NET 8.0 installed on Linux
  • .NET 8.0 installed on Mac OS
  • .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

Security Updates (3)

Acknowledgments

Miha Zupan with Microsoft

Revision History

  • 2026-08-11: Information published.