Open WebUI: Unauthenticated requests can stall the server via uncached OIDC fetches in back-channel logout

{
  "id": "bea14d861dd1442cad801149c9525fa814457b8ddce72c03f1e43be61f212e32",
  "url": "https://osv.dev/vulnerability/CVE-2026-87011",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Open WebUI: Unauthenticated requests can stall the server via uncached OIDC fetches in back-channel logout",
    "summary": "Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.9.0 until 0.11.1, the unauthenticated POST /oauth/backchannel-logout handler in backend/open_webui/utils/oauth.py fetched the OIDC discovery document and signing keys before validating a submitted logout token. Each request repeated uncached network fetches, and the signing-key lookup blocked the async event loop, so requests carrying invalid tokens could stall the single-worker instance and amplify traffic to the identity provider when ENABLE_OAUTH_BACKCHANNEL_LOGOUT was enabled. This issue is fixed in version 0.11.1.",
    "evidence": "osv:CVE-2026-87011",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-87011",
      "aliases": [
        "CVE-2026-87011",
        "GHSA-3g9q-v48f-hh9w",
        "PYSEC-2026-4117"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/open-webui/open-webui",
              "type": "GIT",
              "events": [
                {
                  "introduced": "f31768e20e5c6b4f6da0ef657877298b359936cf"
                },
                {
                  "fixed": "d3e8bf3405e848cfba377814d0aa7ba7290e414d"
                },
                {
                  "fixed": "aeda6ff13a25d3b3ba1b303609f35382db22142c"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:openwebui:open_webui:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0.9.0"
                      },
                      {
                        "fixed": "0.11.1"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "aeda6ff13a25d3b3ba1b303609f35382db22142c"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "d3e8bf3405e848cfba377814d0aa7ba7290e414d"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v0.11.1"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v0.11.0",
            "v0.10.2",
            "v0.10.1",
            "v0.10.0",
            "v0.9.5",
            "v0.9.4",
            "v0.9.3",
            "v0.9.2",
            "v0.9.1",
            "v0.9.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-87011.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:29.938614727Z",
      "provider": "osv",
      "references": [
        "https://github.com/open-webui/open-webui/releases/tag/v0.11.1",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/87xxx/CVE-2026-87011.json",
        "https://github.com/open-webui/open-webui/security/advisories/GHSA-3g9q-v48f-hh9w",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-87011",
        "https://github.com/open-webui/open-webui/commit/aeda6ff13a25d3b3ba1b303609f35382db22142c"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-405",
          "CWE-770"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/87xxx/CVE-2026-87011.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-87011",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 496573,
  "published_at": "2026-09-09T20:54:26.207+00:00"
}