Open WebUI: Channel members can overwrite another member's message via the chat completions endpoint (CVE-2026-87994) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-87994

Open WebUI: Channel members can overwrite another member's message via the chat completions endpoint

Answer in brief

CVE-2026-87994 records a Unknown severity vulnerability in Open WebUI: Channel members can overwrite another member's message via the chat completions endpoint. The current sources do not mark it as known exploited. The current feed maps open-webui/open-webui (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 9, 2026Updated Sep 9, 2026Source checked Sep 9, 2026First seen by HOL Sep 9, 2026Material review Sep 9, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Not reported

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps open-webui/open-webui (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
open-webui/open-webuigeneric	>= 0.9.5, < 0.11.1	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for open-webui/open-webui.
Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

Published upstream
Sep 9, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 9, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 9, 2026

Sources and claim methodology

Upstream source description

Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.9.5 until 0.11.1, the channel branch of chat_completion in backend/open_webui/main.py checked channel write access and channel membership for a supplied message_id but did not verify that the calling user authored the targeted message. A channel member could use the chat completions endpoint to replace another member's message while preserving the victim as the stored author, altering the conversation record without gaining access to other channels. This issue is fixed in version 0.11.1.

Quoted source text, attributed separately from HOL analysis.