Windows Defender Firewall EUVD-2026-73398

Exploitation requires an authenticated local session with a standard (non-administrative) user account on the target Windows system - consistent with CVSS PR:L. The attacker must have the ability to interact with or send requests to the Windows Defender Firewall Service, implying the service must be running (its default state on all affected Windows versions). No network-facing access path is available: the attack vector is strictly local (AV:L). Impact is limited to confidentiality - no write or denial-of-service capability is established by this vulnerability. The scope is unchanged (S:U), meaning the vulnerability does not break out of the firewall service security boundary to affect other system components.

The CVSS 3.1 score of 5.5 (Medium) with vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N appropriately positions this as a local, low-complexity privilege-of-access issue. Real-world risk is moderate: the local attack vector (AV:L) and low-privilege requirement (PR:L) mean an attacker must already have a foothold on the target system, substantially limiting initial-access scenarios. However, the High confidentiality impact (C:H) signals that exposed firewall service files may contain policy configurations or sensitive operational data useful for post-compromise reconnaissance - for example, understanding what network filtering rules are in place before moving laterally. The vulnerability is not listed in CISA KEV and no public exploit code has been identified, reducing immediate exploitation urgency. The 'Path Traversal' tag implies a specific traversal primitive, which typically requires targeted crafting rather than spray-and-pray automation. No EPSS data was provided, so quantitative exploitation probability cannot be stated. This is a meaningful post-access stepping-stone vulnerability rather than a primary attack vector.

A threat actor who has compromised a standard Windows user account on a target system - through phishing or credential theft - uses a path traversal request against the Windows Defender Firewall Service to read firewall policy or configuration files outside the normally accessible directory. The attacker uses this information to map allowed network paths and exceptions before pivoting laterally or escalating privileges. No public exploit code exists at time of analysis, but the low-complexity (AC:L) vector suggests a working exploit would be straightforward to develop once the traversal primitive is identified.