CVE Alert: CVE-2025-59273 – Microsoft – Azure Event Grid System

Risk verdict

High risk due to privilege-elevation potential in a network-accessible cloud service; exploitation status is currently unconfirmed pending KEV/SSVC and EPSS data.

Why this matters

If exploited, attackers could control event routing and data flows within a tenant, undermining isolation and disrupting automated processes. Business impact includes service disruption, data integrity concerns, and events being directed to untrusted endpoints.

Most likely attack path

Attack relies on network access with no credentials or user interaction required (AV:N, UI:N, PR:N). The flaw could elevate privileges in the service control plane, enabling edits to subscriptions or routing while remaining within the same tenant boundary, facilitating targeted impact rather than broad cross-tenant effects.

Who is most exposed

Organisations using Event Grid in public or multi-tenant cloud deployments, especially where subscriptions or endpoints are publicly reachable or integrated with external systems.

Detection ideas

• Unauthorised privilege escalations in the control plane.
• Modifications to event subscriptions or routing targets to new or untrusted endpoints.
• Anomalous API activity from unknown principals or IPs.
• Changes to access policies or roles without corresponding security reviews.
• Control-plane logs showing privileged actions without matching user activity.

Mitigation and prioritisation

• Apply official patch when released; test before production rollout.
• Reduce exposure: enable Private Endpoints, disable public endpoints where feasible, implement IP allowlisting.
• Enforce least privilege; rotate credentials for related service principals.
• Enable detailed auditing and alerts on control-plane activity and subscription changes.
• If KEV true or EPSS ≥ 0.5, treat as priority 1.