.NET Framework CVE-2026-32177

User must open or execute a specially crafted .NET application, assembly (DLL/EXE), or Visual Studio project file from an untrusted source. The vulnerability affects default .NET runtime configurations without requiring specific feature enablement. Exploitation is limited by the local attack vector (AV:L) requiring the malicious file to already be present on the target system through social engineering, removable media, or prior compromise. The mandatory user interaction (UI:R) means automated remote exploitation is not possible - an authenticated or unauthenticated user must actively trigger the vulnerability by launching the malicious .NET content. Windows systems with .NET Framework or .NET runtime installed are vulnerable regardless of whether they are developer machines or end-user workstations.

Real-world risk is moderate-high for multi-user Windows environments where users handle untrusted .NET applications or documents. The CVSS 7.3 score reflects local attack vector with low complexity (AV:L/AC:L), but critically requires no prior privileges (PR:N) and mandatory user interaction (UI:R). This profile suggests phishing or social engineering delivery of malicious .NET binaries rather than remote network exploitation. No EPSS score, KEV listing, or public POC data is provided, suggesting limited observed exploitation at analysis time - likely a proactive vendor disclosure. The PR:N metric is significant: attackers start from unprivileged context, making this valuable for initial access scenarios where code execution leads to privilege escalation. Primary risk is for systems where users regularly execute .NET applications from external sources (email attachments, downloads, removable media). Developer workstations running Visual Studio 2017 face additional risk when opening third-party projects. The UI:R requirement provides defensive opportunity through user awareness training, though sophisticated attackers can disguise malicious payloads as legitimate documents.

Attacker crafts a malicious .NET assembly or Visual Studio project file containing heap overflow triggers in metadata or resource structures. Delivery via phishing email with attachment labeled as invoice, report, or software tool convinces target user to execute the file. Upon opening, the .NET runtime processes the malformed data, overflowing a heap buffer and allowing attacker-controlled memory corruption. Exploitation achieves code execution in the context of the .NET process, then leverages the PR:N→High privileges transition to escalate from standard user to SYSTEM-level access, enabling persistent malware installation or credential theft.