CVE Alert: CVE-2025-55247 – Microsoft – .NET 8.0

Risk verdict

High risk of local privilege escalation in .NET components; patching should be prioritised even though public exploitation evidence is not observed.

Why this matters

If exploited, an attacker could gain total control from a low-privilege state via link-following in .NET, enabling data theft, tampering or persistence. The combination of a high base impact and the need for user interaction means breaches are feasible in environments where users routinely open links or files.

Most likely attack path

An attacker must already have local access and induce user interaction (UI:R) to trigger the chain. The flaw grants elevation from a user with low privileges (PR:L) to a higher-privilege context, once a user opens a crafted link or file, due to improper link resolution. Lateral movement depends on the attacker’s ability to exploit trusted processes within the user’s session.

Who is most exposed

Endpoints and servers running affected .NET 8.x or 9.x installations are at risk, particularly where users operate with standard privileges and may interact with external content. Organisations with internal apps or desktop/mobile clients built on these runtimes are especially exposed.

Detection ideas

• Look for unusual dotnet process activity following user-initiated file/link interactions.
• Correlate unexpected file access attempts or elevated operations after UI-triggered events.
• Monitor for privilege escalation patterns from standard users to admin-level tokens.
• Inspect application logs for anomalous link-resolution or file-access sequences.
• Correlate with anomalous network or file-system activity post-interaction.

Mitigation and prioritisation

• Apply the fixed releases: update to the supported versions (8.0.21 and 9.0.10) across all affected systems.
• Enforce least-privilege: limit admin rights, and implement application whitelisting (e.g., WDAC/Applocker) and strong identity controls.
• Accelerate change-management: plan a tested, organisation-wide patch window within the next cycle; verify via asset inventory and baseline checks.
• Contain risk with compensating controls: segment critical assets, monitor for privilege-escalation indicators, and disable or restrict high-risk content delivery channels.