What happened
Open WebUI, a widely-deployed self-hosted AI chat platform, contains CVE-2026-59714 (CVSS 7.1, High): from 0.9.5 before 0.10.0, any authenticated user can overwrite the content of a message in a channel they do not belong to — including private and DM channels — by sending a chat completion request with a crafted channel-prefixed parameter.
Why it matters
Open WebUI is one of the most popular open-source front-ends for self-hosted LLM deployments; this flaw breaks channel-level access isolation, letting any authenticated user tamper with private/DM conversation content across the entire instance, undermining confidentiality and integrity guarantees for multi-tenant deployments.
Attack vector
Authenticated user sends a chat completion request with a channel:-prefixed parameter targeting a channel they are not a member of, overwriting message content in that channel including private/DM channels
Affected systems
Open WebUI 0.9.5 to < 0.10.0
Mitigation
Upgrade to Open WebUI 0.10.0 or later