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CVE-2026-28788

Status: AnalyzedHigh (7.1)—

Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to version 0.8.6, any authenticated user can overwrite any file's content by ID through the `POST /api/v1/retrieval/process/files/batch` endpoint. The endpoint performs no ownership check, so a regular user with read access to a shared knowledge base can obtain file UUIDs via `GET /api/v1/knowledge/{id}/files` and then overwrite those files, escalating from read to write. The overwritten content is served to the LLM via RAG, meaning the attacker controls what the model tells other users. Version 0.8.6 patches the issue.

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

Acceso autenticado en red sin privilegios especiales (PR:L) para modificar archivos. T1210 de servicios remotos. Impacto: manipulación de datos RAG (T1565.001) servidos al LLM; escalada de acceso de lectura a escritura (T1078.001 abuso de cuentas legítimas con permisos insuficientes validados).

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Vulnerability ScanningThreat Intelligence ProgramRestrict File and Directory PermissionsPrivileged Account ManagementPassword PoliciesRemote Data Storage

Affected technologies (1)

Openwebui — Open Webui

CWEs

References

Raw JSON (NVD)

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