CVE-2026-62915

The 'authorized attacker' qualifier in CVE-2026-62915 is doing the opposite of what it appears to do. It doesn't narrow the blast radius — it defers the blast radius calculation to a future date when organizational access patterns have shifted. That's the critical insight this disclosure requires: the population of 'authorized' users in an Exchange environment is not static. Service accounts get provisioned, admin permissions expand to new teams during incident response, and OWA exposure grows during business continuity events. Every month this authorization bypass sits unpatched, the attack surface it represents quietly compounds. The EPSS score of 0.00494 measures current weaponization likelihood — and that's a trailing indicator. This class of flaw (authorization bypass in a credential store) has a documented genealogical pattern: rated medium, deferred to normal patch cycles, then surfaces six to eighteen months later in incident retrospectives as the pivot mechanism that turned a compromised service account into domain-level compromise. The pattern isn't coincidental — it reflects CVSS measuring impact severity at a single point in time while the real risk window extends and compounds as the environment changes around the unpatched vulnerability. Your priorities: First, determine which user classes can trigger this bypass. If it affects any standard mailbox user with OWA access, the blast radius is the entire active user population — not a narrow privileged enclave. Second, audit your service accounts with Exchange permissions, because a compromised service account with cross-server or hybrid AD integration turns a contained compromise into infrastructure-wide exposure. Third, recognize that your existing detection stack is likely blind to this. Most SIEM playbooks monitor authentication anomalies and suspicious OAuth grants — they don't watch for 'user A accessed feature X they shouldn't have access to' because that requires knowing what features exist and who should use them. A missing authorization check is invisible to most environments until post-compromise analysis surfaces it. Treat this as 'patch in the next cycle, but instrument the authorization layer now.' Document which accounts have Exchange access, review delegation patterns, and prepare detection logic for anomalous feature access — because when this CVE eventually shows up in a retrospective, you want the answer to 'what did this do to their existing capabilities' to be documented before the incident, not reverse-engineered after it.

Reviewed through automated stages and approved by a human before publication.