Microsoft .NET Framework CVE-2026-108398

Requires an authorized, authenticated attacker with local low-privileged access (AV:L/PR:L) and the ability to write a malicious file/library into a directory that the .NET Framework resolves ahead of the legitimate path (untrusted search path, CWE-426). No user interaction is needed (UI:N). Limiting factors that reduce real-world risk: there is no remote/network vector, the attacker must already hold a local foothold with some privilege, and must be able to influence a writable directory in the DLL/assembly search order; SSVC reports no observed exploitation and rates it non-automatable. Affected builds span .NET Framework 3.5, 4.6.2-4.7.2, 4.8, and 4.8.1 below the fixed revisions listed in the EUVD data, so patch level is a determining factor.

Signals conflict on urgency. The CVSS base score of 8.8 (HIGH) is driven by a changed scope (S:C) and total impact (C:H/I:H/A:H), but the vector itself is constrained: AV:L means the attacker must already be local, AC:L is low complexity, and PR:L confirms an authenticated/authorized foothold is required before exploitation. CISA's SSVC framework reinforces a lower real-world priority - Exploitation: none (no observed activity), Automatable: no (cannot be reliably scripted at scale), though Technical Impact: total aligns with the high CIA metrics. There is no CISA KEV listing and no EPSS score was provided, so exploitation probability cannot be quantified; no public exploit was identified at time of analysis. Net assessment: this is a high-severity-but-local post-compromise privilege/security-boundary issue, not an internet-facing emergency. It matters most as an escalation primitive on already-breached hosts rather than a mass-exploitation threat. Patch promptly on a normal cadence; the AV:L + PR:L + SSVC-no-exploitation combination argues against treating it as a drop-everything remote threat.

An attacker who already has low-privileged authenticated access to a Windows host places a malicious library in a directory that the .NET Framework searches before the legitimate location (CWE-426, untrusted search path). When a .NET process loads the planted component, the attacker's code runs in that process context, bypassing an intended security feature and escalating control. No public exploit code was identified at time of analysis, and the local attack vector (AV:L) means remote triggering is not possible.