Microsoft Entra ID EUVD-2026-63693

The CVSS vector is AV:N/AC:L/PR:N/UI:N, so no authentication, no user interaction, and no special client-side conditions are required - exploitation is unauthenticated and remote against a reachable Entra ID deserialization endpoint. The concrete prerequisite from the description is that the attacker must be able to deliver untrusted serialized data to a network-facing component that deserializes it (CWE-502). The main limiting factor is exposure and reachability of the vulnerable endpoint plus Microsoft's service-side patch state: because Entra ID is a vendor-operated cloud service, remediation may already be applied centrally, which would substantially constrain real-world exploitability regardless of the maximal CVSS score.

Every raw signal points to top-tier severity: the CVSS 3.1 vector AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H yields a perfect 10.0, meaning low-complexity, unauthenticated, no-interaction network exploitation with full impact and scope change. The offsetting nuance is that EPSS is not provided, the CVE is not in CISA KEV, and no proof-of-concept is referenced, so there is no evidence of active exploitation or automatable mass-scanning yet - this is currently a high-theoretical-severity issue rather than a confirmed in-the-wild campaign. Because Entra ID is a cloud service that Microsoft operates and patches centrally, real-world tenant exposure depends heavily on whether Microsoft has already remediated the service side; organizations should nonetheless treat any RCE in their identity provider as an emergency and verify the vendor advisory rather than assume automatic protection. Given that a compromise of the identity layer can cascade into every federated application, defenders should prioritize this immediately and confirm remediation status directly with Microsoft.

An unauthenticated attacker crafts a malicious serialized payload and sends it over the network to an exposed Entra ID endpoint that deserializes the input, triggering execution of attacker-controlled code within the identity service context. Because no authentication or user interaction is required (PR:N/UI:N) and complexity is low, a single crafted request could suffice; with scope change, successful execution could reach resources beyond the initial component. No public proof-of-concept is referenced at time of analysis.