Breaking Down Nextcloud CVE-2026-45281 🔓 An authenticated attacker knowing a user’s principal URL shouldn't mean total control over their calendar. Yet, that’s precisely what CVE-2026-45281 a high-severity authorization flaw in Nextcloud Server allows. Breaking down this cross-account calendar takeover: 🟢The Root Cause: Improper authorization controls ([CWE-639]) in the calendar backend fail to verify if the requesting user actually owns or has access to the target principal URL. 🟢 The Impact: Full read and write access across multi-tenant deployments, allowing malicious actors to view, create, modify, or delete sensitive calendar events. 👉 Read our full research breakdown to understand the attack vector, detection strategies, and mitigation steps: https://ethiack.com/info-hub/research/nextcloud-cve-2026-45281
Post summary
The post provides a technical breakdown of Nextcloud CVE‑2026‑45281, outlining the root cause, impact, and mitigation steps, but does not present a PoC, exploit code, or evidence of active exploitation.
