Open WebUI CVE-2026-109297

Requires an authenticated account holding the 'permitted to create automations' privilege (CVSS PR:L) - exploitation is impossible for fully unauthenticated attackers. The attacker must submit a recurrence rule that defeats the sub-daily frequency guard, concretely by whitespace-folding the rule text, or on version 0.11.0 specifically by using lowercase frequency keywords or omitting the RRULE prefix so the stricter validator and the executing calendar library diverge. Limiting factors: the flaw is confined to the automation recurrence-rule feature, impact is availability-only (no data exposure or modification), and real-world reach depends on how broadly automation-creation rights are granted - admin-only automation roles sharply reduce exposure, while instances that let ordinary users create automations are directly at risk. Patched in 0.11.4.

This is a moderate, authentication-gated availability threat rather than a top-tier emergency. The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H) scores 7.1 and is internally consistent with the description: network-reachable, low complexity, but requiring low-level privileges - specifically a user already permitted to create automations - with impact confined entirely to availability (VA:H; no confidentiality or integrity effect). No EPSS score was supplied and the vulnerability is not in CISA KEV, so there is no confirmed active exploitation; no public exploit code was referenced either, making this 'no public exploit identified at time of analysis.' The SSVC-style read is low urgency: exploitation is not observed, technical impact is partial (DoS only), and while the per-second RRULE expansion is mechanically simple to trigger, it is not internet-wide automatable because an attacker must first hold a privileged automation-creation role. The main caveat is that PR:L depends on the deployment's authorization model - if automation creation is broadly granted to ordinary users (a common convenience configuration), the practical barrier is low; if restricted to admins, real-world risk drops further. Overall: a real but manageable DoS, prioritize patching for multi-user/shared instances over single-user deployments.

An authenticated user with automation-creation rights submits a recurrence rule that evades the sub-daily frequency guard via whitespace folding (or, on 0.11.0, lowercase frequencies or a missing RRULE prefix), causing the calendar library to expand it per-second. The synchronous expansion blocks the shared event loop for minutes on the triggering request and again on every scheduler poll, denying service to all other users. No public proof-of-concept was referenced, but the trigger is simple to craft from the description.