#.NET and Visual Studio

**How could an attacker exploit this vulnerability?** A remote unauthenticated attacker could exploit this vulnerability by sending specially crafted requests to a vulnerable .NET webapp or by loading a specially crafted file into a vulnerable desktop app.

**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 an attacker to win a race condition.

**What type of information could be disclosed by this vulnerability?** An attacker who successfully exploited the vulnerability could read targeted email messages.

**.NET 6.0 was added to the Security Updates table on October 8, 2024 because it is also affected by this vulnerability. Why are the Download and Article links missing for .NET 6.0?** HTTP/3 support was only experimental in .NET 6.0. If you are using .NET 6 you must update your application to .NET 8 to be protected. Experimental features will not be patched if a later runtime includes the feature as non-experimental..

**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 an attacker to win a race condition.

**What privileges could be gained by an attacker who successfully exploited this vulnerability?** An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.

**According to the CVSS metrics, successful exploitation of this vulnerability could lead to minor loss of confidentiality (C:L), integrity (I:L) and availability (A:L). What does that mean for this vulnerability?** While we cannot rule out the impact to Confidentiality, Integrity, and Availability, the ability to exploit this vulnerability by itself is limited. An attacker would need to combine this with other vulnerabilities to perform an attack.

**According to the CVSS metric, the attack vector is local (AV:L). Why does the CVE title indicate that this is a remote code execution?** The word **Remote** in the title refers to the location of the attacker. This type of exploit is sometimes referred to as Arbitrary Code Execution (ACE). The attack itself is carried out locally. This means an attacker or victim needs to execute code from the local machine to exploit the vulnerability.

**What kind of security feature could be bypassed by successfully exploiting this vulnerability?** A security feature bypass vulnerability exists when Microsoft .NET Framework-based applications use X.509 chain building APIs but do not completely validate the X.509 certificate due to a logic flaw. An attacker could present an arbitrary untrusted certificate with malformed signatures, triggering a bug in the framework. The framework will correctly report that X.509 chain building failed, but it will return an incorrect reason code for the failure. Applications which utilize this reason code to make their own chain building trust decisions may inadvertently treat this scenario as a successful chain build. This could allow an adversary to subvert the app's typical authentication logic.

**According to the CVSS metric, user interaction is required (UI:R). What interaction would the user have to do?** Exploitation of this vulnerability requires that an attacker convinces a user to open a maliciously crafted package file in Visual Studio.