Vulnerability-Lookup

CVE-2026-87011 (GCVE-0-2026-87011)

Vulnerability from cvelistv5 – Published: 2026-09-09 20:54 – Updated: 2026-09-14 13:42

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.

Severity

7.5 (High)


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

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-14 13:41 UTC

CWE

CWE-405 - Asymmetric Resource Consumption (Amplification)
CWE-770 - Allocation of Resources Without Limits or Throttling

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7771 records in the last 180 days details

References

3 references

URL	Tags
https://github.com/open-webui/open-webui/security…	x_refsource_CONFIRM
https://github.com/open-webui/open-webui/commit/a…	x_refsource_MISC
https://github.com/open-webui/open-webui/releases…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
open-webui	open-webui	Affected: >= 0.9.0, < 0.11.1	guessed

Show details on NVD website

JSON

To clipboard

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BDU:2026-14479 (CVE-2026-87011)

Vulnerability from fstec – Published: 2026-09-10 – Updated: 2026-09-11 – View on bdu.fstec.ru Exploit publicly available Fixed

Title

Уязвимость обработчика /oauth/backchannel-logout веб-интерфейса на базе искуственного интеллекта Open WebUI, позволяющая нарушителю вызвать отказ в обслуживании

Summary

Уязвимость обработчика /oauth/backchannel-logout веб-интерфейса на базе искуственного интеллекта Open WebUI связана с асимметричным потреблением ресурсов. Эксплуатация уязвимости может позволить нарушителю, действующему удалённо, вызвать отказ в обслуживании

Severity

7.8 (High) CVSS 2.0


                      
                        AV:N/AC:L/Au:N/C:N/I:N/A:C

7.5 (High) CVSS 3.1


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

Class

Code vulnerability

Status

Confirmed by the vendor

Exploitation

Resource exhaustion

Incidents

Being clarified

Remediation

Software update

CWE

CWE-405 - Асимметричное потребление ресурсов (Усиление)
CWE-770 - Неограниченное распределение ресурсов или дросселирование

Aliases

CVE-2026-87011, GHSA-3G9Q-V48F-HH9W

References

3 references

URL
https://github.com/open-webui/open-webui/releases/tag/v0.11.1
https://github.com/open-webui/open-webui/commit/aeda6ff13a25d3b3ba1b303609f3538…
https://github.com/open-webui/open-webui/security/advisories/GHSA-3g9q-v48f-hh9w

Impacted products

1 product from 1 vendor

Vendors

Сообщество свободного программного обеспечения

Products

Open WebUI

Versions

от 0.9.0 до 0.11.0 включительно (Open WebUI)

Product types

Application software, AI development software

Mitigations

Использование рекомнедаций производителя: https://github.com/open-webui/open-webui/releases/tag/v0.11.1

JSON

To clipboard

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  "CVSS 4.0": null,
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  "\u0418\u0434\u0435\u043d\u0442\u0438\u0444\u0438\u043a\u0430\u0442\u043e\u0440": "BDU:2026-14479",
  "\u0418\u0434\u0435\u043d\u0442\u0438\u0444\u0438\u043a\u0430\u0442\u043e\u0440\u044b \u0434\u0440\u0443\u0433\u0438\u0445 \u0441\u0438\u0441\u0442\u0435\u043c \u043e\u043f\u0438\u0441\u0430\u043d\u0438\u0439 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": "CVE-2026-87011, GHSA-3g9q-v48f-hh9w",
  "\u0418\u043d\u0444\u043e\u0440\u043c\u0430\u0446\u0438\u044f \u043e\u0431 \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0438\u0438": "\u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0430",
  "\u041a\u043b\u0430\u0441\u0441 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": "\u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u043a\u043e\u0434\u0430",
  "\u041d\u0430\u0437\u0432\u0430\u043d\u0438\u0435 \u041f\u041e": "Open WebUI",
  "\u041d\u0430\u0438\u043c\u0435\u043d\u043e\u0432\u0430\u043d\u0438\u0435 \u041e\u0421 \u0438 \u0442\u0438\u043f \u0430\u043f\u043f\u0430\u0440\u0430\u0442\u043d\u043e\u0439 \u043f\u043b\u0430\u0442\u0444\u043e\u0440\u043c\u044b": null,
  "\u041d\u0430\u0438\u043c\u0435\u043d\u043e\u0432\u0430\u043d\u0438\u0435 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": "\u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u043e\u0431\u0440\u0430\u0431\u043e\u0442\u0447\u0438\u043a\u0430 /oauth/backchannel-logout \u0432\u0435\u0431-\u0438\u043d\u0442\u0435\u0440\u0444\u0435\u0439\u0441\u0430 \u043d\u0430 \u0431\u0430\u0437\u0435 \u0438\u0441\u043a\u0443\u0441\u0442\u0432\u0435\u043d\u043d\u043e\u0433\u043e \u0438\u043d\u0442\u0435\u043b\u043b\u0435\u043a\u0442\u0430 Open WebUI, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u043d\u0430\u0440\u0443\u0448\u0438\u0442\u0435\u043b\u044e \u0432\u044b\u0437\u0432\u0430\u0442\u044c \u043e\u0442\u043a\u0430\u0437 \u0432 \u043e\u0431\u0441\u043b\u0443\u0436\u0438\u0432\u0430\u043d\u0438\u0438",
  "\u041d\u0430\u043b\u0438\u0447\u0438\u0435 \u044d\u043a\u0441\u043f\u043b\u043e\u0439\u0442\u0430": "\u0421\u0443\u0449\u0435\u0441\u0442\u0432\u0443\u0435\u0442 \u0432 \u043e\u0442\u043a\u0440\u044b\u0442\u043e\u043c \u0434\u043e\u0441\u0442\u0443\u043f\u0435",
  "\u041e\u043f\u0438\u0441\u0430\u043d\u0438\u0435 \u043e\u0448\u0438\u0431\u043a\u0438 CWE": "\u0410\u0441\u0438\u043c\u043c\u0435\u0442\u0440\u0438\u0447\u043d\u043e\u0435 \u043f\u043e\u0442\u0440\u0435\u0431\u043b\u0435\u043d\u0438\u0435 \u0440\u0435\u0441\u0443\u0440\u0441\u043e\u0432 (\u0423\u0441\u0438\u043b\u0435\u043d\u0438\u0435) (CWE-405), \u041d\u0435\u043e\u0433\u0440\u0430\u043d\u0438\u0447\u0435\u043d\u043d\u043e\u0435 \u0440\u0430\u0441\u043f\u0440\u0435\u0434\u0435\u043b\u0435\u043d\u0438\u0435 \u0440\u0435\u0441\u0443\u0440\u0441\u043e\u0432 \u0438\u043b\u0438 \u0434\u0440\u043e\u0441\u0441\u0435\u043b\u0438\u0440\u043e\u0432\u0430\u043d\u0438\u0435 (CWE-770)",
  "\u041e\u043f\u0438\u0441\u0430\u043d\u0438\u0435 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": "\u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u043e\u0431\u0440\u0430\u0431\u043e\u0442\u0447\u0438\u043a\u0430 /oauth/backchannel-logout \u0432\u0435\u0431-\u0438\u043d\u0442\u0435\u0440\u0444\u0435\u0439\u0441\u0430 \u043d\u0430 \u0431\u0430\u0437\u0435 \u0438\u0441\u043a\u0443\u0441\u0442\u0432\u0435\u043d\u043d\u043e\u0433\u043e \u0438\u043d\u0442\u0435\u043b\u043b\u0435\u043a\u0442\u0430 Open WebUI \u0441\u0432\u044f\u0437\u0430\u043d\u0430 \u0441 \u0430\u0441\u0438\u043c\u043c\u0435\u0442\u0440\u0438\u0447\u043d\u044b\u043c \u043f\u043e\u0442\u0440\u0435\u0431\u043b\u0435\u043d\u0438\u0435\u043c \u0440\u0435\u0441\u0443\u0440\u0441\u043e\u0432. \u042d\u043a\u0441\u043f\u043b\u0443\u0430\u0442\u0430\u0446\u0438\u044f \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438 \u043c\u043e\u0436\u0435\u0442 \u043f\u043e\u0437\u0432\u043e\u043b\u0438\u0442\u044c \u043d\u0430\u0440\u0443\u0448\u0438\u0442\u0435\u043b\u044e, \u0434\u0435\u0439\u0441\u0442\u0432\u0443\u044e\u0449\u0435\u043c\u0443 \u0443\u0434\u0430\u043b\u0451\u043d\u043d\u043e, \u0432\u044b\u0437\u0432\u0430\u0442\u044c \u043e\u0442\u043a\u0430\u0437 \u0432 \u043e\u0431\u0441\u043b\u0443\u0436\u0438\u0432\u0430\u043d\u0438\u0438",
  "\u041f\u043e\u0441\u043b\u0435\u0434\u0441\u0442\u0432\u0438\u044f \u044d\u043a\u0441\u043f\u043b\u0443\u0430\u0442\u0430\u0446\u0438\u0438 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": null,
  "\u041f\u0440\u043e\u0447\u0430\u044f \u0438\u043d\u0444\u043e\u0440\u043c\u0430\u0446\u0438\u044f": null,
  "\u0421\u0432\u044f\u0437\u044c \u0441 \u0438\u043d\u0446\u0438\u0434\u0435\u043d\u0442\u0430\u043c\u0438 \u0418\u0411": "\u0414\u0430\u043d\u043d\u044b\u0435 \u0443\u0442\u043e\u0447\u043d\u044f\u044e\u0442\u0441\u044f",
  "\u0421\u043e\u0441\u0442\u043e\u044f\u043d\u0438\u0435 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": "\u041e\u043f\u0443\u0431\u043b\u0438\u043a\u043e\u0432\u0430\u043d\u0430",
  "\u0421\u043f\u043e\u0441\u043e\u0431 \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0438\u044f": "\u041e\u0431\u043d\u043e\u0432\u043b\u0435\u043d\u0438\u0435 \u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c\u043d\u043e\u0433\u043e \u043e\u0431\u0435\u0441\u043f\u0435\u0447\u0435\u043d\u0438\u044f",
  "\u0421\u043f\u043e\u0441\u043e\u0431 \u044d\u043a\u0441\u043f\u043b\u0443\u0430\u0442\u0430\u0446\u0438\u0438": "\u0418\u0441\u0447\u0435\u0440\u043f\u0430\u043d\u0438\u0435 \u0440\u0435\u0441\u0443\u0440\u0441\u043e\u0432",
  "\u0421\u0441\u044b\u043b\u043a\u0438 \u043d\u0430 \u0438\u0441\u0442\u043e\u0447\u043d\u0438\u043a\u0438": "https://github.com/open-webui/open-webui/releases/tag/v0.11.1\nhttps://github.com/open-webui/open-webui/commit/aeda6ff13a25d3b3ba1b303609f35382db22142c\nhttps://github.com/open-webui/open-webui/security/advisories/GHSA-3g9q-v48f-hh9w",
  "\u0421\u0442\u0430\u0442\u0443\u0441 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": "\u041f\u043e\u0434\u0442\u0432\u0435\u0440\u0436\u0434\u0435\u043d\u0430 \u043f\u0440\u043e\u0438\u0437\u0432\u043e\u0434\u0438\u0442\u0435\u043b\u0435\u043c",
  "\u0422\u0438\u043f \u041f\u041e": "\u041f\u0440\u0438\u043a\u043b\u0430\u0434\u043d\u043e\u0435 \u041f\u041e \u0438\u043d\u0444\u043e\u0440\u043c\u0430\u0446\u0438\u043e\u043d\u043d\u044b\u0445 \u0441\u0438\u0441\u0442\u0435\u043c, \u041f\u041e \u0434\u043b\u044f \u0440\u0430\u0437\u0440\u0430\u0431\u043e\u0442\u043a\u0438 \u0418\u0418",
  "\u0422\u0438\u043f \u043e\u0448\u0438\u0431\u043a\u0438 CWE": "CWE-405, CWE-770",
  "\u0423\u0440\u043e\u0432\u0435\u043d\u044c \u043e\u043f\u0430\u0441\u043d\u043e\u0441\u0442\u0438 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": "\u0412\u044b\u0441\u043e\u043a\u0438\u0439 \u0443\u0440\u043e\u0432\u0435\u043d\u044c \u043e\u043f\u0430\u0441\u043d\u043e\u0441\u0442\u0438 (\u0431\u0430\u0437\u043e\u0432\u0430\u044f \u043e\u0446\u0435\u043d\u043a\u0430 CVSS 2.0 \u0441\u043e\u0441\u0442\u0430\u0432\u043b\u044f\u0435\u0442 7,8)\n\u0412\u044b\u0441\u043e\u043a\u0438\u0439 \u0443\u0440\u043e\u0432\u0435\u043d\u044c \u043e\u043f\u0430\u0441\u043d\u043e\u0441\u0442\u0438 (\u0431\u0430\u0437\u043e\u0432\u0430\u044f \u043e\u0446\u0435\u043d\u043a\u0430 CVSS 3.1 \u0441\u043e\u0441\u0442\u0430\u0432\u043b\u044f\u0435\u0442 7,5)"
}

FKIE_CVE-2026-87011

Vulnerability from fkie_nvd - Published: 2026-09-09 21:17 - Updated: 2026-09-15 16:26

Severity

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

Summary

References

URL	Tags
security-advisories@github.com	https://github.com/open-webui/open-webui/commit/aeda6ff13a25d3b3ba1b303609f35382db22142c	Patch
security-advisories@github.com	https://github.com/open-webui/open-webui/releases/tag/v0.11.1	Release Notes
security-advisories@github.com	https://github.com/open-webui/open-webui/security/advisories/GHSA-3g9q-v48f-hh9w	Exploit, Vendor Advisory
134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/open-webui/open-webui/security/advisories/GHSA-3g9q-v48f-hh9w	Exploit, Vendor Advisory

Impacted products

	Vendor	Product	Version
	openwebui	open_webui	*

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "open-webui",
          "vendor": "open-webui",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 0.9.0, \u003c 0.11.1"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:openwebui:open_webui:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "7E28CB04-D68C-4671-9F9B-511FA13EDB5C",
              "versionEndExcluding": "0.11.1",
              "versionStartIncluding": "0.9.0",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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."
    }
  ],
  "id": "CVE-2026-87011",
  "lastModified": "2026-09-15T16:26:18.880",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-87011",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-09-14T13:41:36.439676Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-09-09T21:17:05.847",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/open-webui/open-webui/commit/aeda6ff13a25d3b3ba1b303609f35382db22142c"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://github.com/open-webui/open-webui/releases/tag/v0.11.1"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/open-webui/open-webui/security/advisories/GHSA-3g9q-v48f-hh9w"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/open-webui/open-webui/security/advisories/GHSA-3g9q-v48f-hh9w"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-405"
        },
        {
          "lang": "en",
          "value": "CWE-770"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-3G9Q-V48F-HH9W

Vulnerability from github – Published: 2026-09-10 22:44 – Updated: 2026-09-10 22:44

Summary

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

Details

Summary

The OIDC back-channel logout endpoint is unauthenticated by design, because the identity provider calls it without a browser session. Before checking whether the submitted logout token was genuine, the handler fetched the provider's discovery document and its signing keys over the network, and repeated both fetches on every request because nothing was cached. The signing-key fetch also ran as a blocking call inside the async event loop. A small number of requests carrying a worthless token was therefore enough to make the whole instance stop answering.

Preconditions

ENABLE_OAUTH_BACKCHANNEL_LOGOUT=true. The default is False, so a stock deployment is not affected. This setting is recommended in the Open WebUI hardening documentation, which is why the issue is treated as in scope.
At least one OIDC provider configured (OAUTH_CLIENT_ID, OAUTH_CLIENT_SECRET, OPENID_PROVIDER_URL).
No account, credential, session or secret identifier is required. The attacker needs network access to the instance and the configured issuer string, which is published in the provider's own discovery document.

Impact

Against 0.11.0, with the identity provider answering in 150 ms, 60 concurrent requests carrying a token whose signature was four characters long stalled the async event loop for 8.3 seconds, measured against an idle baseline of 10.8 ms. For the length of that stall the process answers nothing: no chat requests, no API calls, no health check. Open WebUI runs a single worker by default, so the effect is instance-wide rather than per-connection, and no rate limit sits in front of the endpoint.

The same traffic is also amplified outward: 20 sequential requests produced 20 discovery fetches and 40 key-set fetches at the identity provider, so an attacker can drive load onto the provider through the instance.

No data is read, modified or exposed, and the forged token is still rejected. The cost is paid before the rejection.

Fix

Fixed in 0.11.1. The handler now resolves both the discovery document and the signing keys through the already-configured OAuth client, so each is fetched once per provider and reused afterwards, and both fetches are asynchronous rather than blocking the event loop. A token carrying no kid header is rejected before any key lookup happens. Upgrading is sufficient, and no configuration change is required.

Root cause

Affected component: the OIDC back-channel logout handler in backend/open_webui/utils/oauth.py, reached through POST /oauth/backchannel-logout. Affected setups: releases 0.9.0 through 0.11.0 with back-channel logout enabled and an OIDC provider configured.

The handler treated its network work as cheap preparation rather than as work worth protecting. For every request it opened a new HTTP session per configured provider to re-read the discovery document, then constructed a fresh JWKS client, whose own cache consequently started empty each time, and asked that client for the signing key through a synchronous call issued directly on the event loop. All of this ran before the token signature was verified, so an attacker unable to produce a valid token still cost the server two network round trips and a blocked loop per request. Both fetches used the library default timeout of five minutes.

Proof of concept

Reproduced by running the unmodified handler from the 0.11.0 and 0.11.1 backends against a loopback identity provider that counted every inbound request and could answer with a configured delay. The submitted token carried a valid issuer and audience, a kid naming a key the provider does not hold, and AAAA as its signature.

20 sequential requests, provider answering immediately:

Version	Discovery fetches	Key-set fetches	Response
0.11.0	20	40	400
0.11.1	1	1	400

60 concurrent requests, provider answering in 150 ms:

Version	Wall time	Discovery fetches	Key-set fetches	Worst event-loop stall
0.11.0	18.6 s	60	120	8255 ms
0.11.1	under 0.01 s	0	0	none measurable

Idle event-loop stall was 10.8 ms in both cases. On 0.11.1 the first request an instance receives warms both caches, and every request after that reaches the signature check without any outbound network call.

Credits

@galanko, for reporting the issue and identifying both the missing caching and the blocking call.

Severity

7.5 (High)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.11.0"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "open-webui"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.9.0"
            },
            {
              "fixed": "0.11.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-87011"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-405",
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-10T22:44:42Z",
    "nvd_published_at": "2026-09-09T21:17:05Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nThe OIDC back-channel logout endpoint is unauthenticated by design, because the identity provider calls it without a browser session. Before checking whether the submitted logout token was genuine, the handler fetched the provider\u0027s discovery document and its signing keys over the network, and repeated both fetches on every request because nothing was cached. The signing-key fetch also ran as a blocking call inside the async event loop. A small number of requests carrying a worthless token was therefore enough to make the whole instance stop answering.\n\n## Preconditions\n\n- `ENABLE_OAUTH_BACKCHANNEL_LOGOUT=true`. The default is `False`, so a stock deployment is not affected. This setting is recommended in the Open WebUI hardening documentation, which is why the issue is treated as in scope.\n- At least one OIDC provider configured (`OAUTH_CLIENT_ID`, `OAUTH_CLIENT_SECRET`, `OPENID_PROVIDER_URL`).\n- No account, credential, session or secret identifier is required. The attacker needs network access to the instance and the configured issuer string, which is published in the provider\u0027s own discovery document.\n\n## Impact\n\nAgainst 0.11.0, with the identity provider answering in 150 ms, 60 concurrent requests carrying a token whose signature was four characters long stalled the async event loop for 8.3 seconds, measured against an idle baseline of 10.8 ms. For the length of that stall the process answers nothing: no chat requests, no API calls, no health check. Open WebUI runs a single worker by default, so the effect is instance-wide rather than per-connection, and no rate limit sits in front of the endpoint.\n\nThe same traffic is also amplified outward: 20 sequential requests produced 20 discovery fetches and 40 key-set fetches at the identity provider, so an attacker can drive load onto the provider through the instance.\n\nNo data is read, modified or exposed, and the forged token is still rejected. The cost is paid before the rejection.\n\n## Fix\n\nFixed in 0.11.1. The handler now resolves both the discovery document and the signing keys through the already-configured OAuth client, so each is fetched once per provider and reused afterwards, and both fetches are asynchronous rather than blocking the event loop. A token carrying no `kid` header is rejected before any key lookup happens. Upgrading is sufficient, and no configuration change is required.\n\n## Root cause\n\nAffected component: the OIDC back-channel logout handler in `backend/open_webui/utils/oauth.py`, reached through `POST /oauth/backchannel-logout`. Affected setups: releases 0.9.0 through 0.11.0 with back-channel logout enabled and an OIDC provider configured.\n\nThe handler treated its network work as cheap preparation rather than as work worth protecting. For every request it opened a new HTTP session per configured provider to re-read the discovery document, then constructed a fresh JWKS client, whose own cache consequently started empty each time, and asked that client for the signing key through a synchronous call issued directly on the event loop. All of this ran before the token signature was verified, so an attacker unable to produce a valid token still cost the server two network round trips and a blocked loop per request. Both fetches used the library default timeout of five minutes.\n\n## Proof of concept\n\nReproduced by running the unmodified handler from the 0.11.0 and 0.11.1 backends against a loopback identity provider that counted every inbound request and could answer with a configured delay. The submitted token carried a valid issuer and audience, a `kid` naming a key the provider does not hold, and `AAAA` as its signature.\n\n20 sequential requests, provider answering immediately:\n\n| Version | Discovery fetches | Key-set fetches | Response |\n| --- | --- | --- | --- |\n| 0.11.0 | 20 | 40 | 400 |\n| 0.11.1 | 1 | 1 | 400 |\n\n60 concurrent requests, provider answering in 150 ms:\n\n| Version | Wall time | Discovery fetches | Key-set fetches | Worst event-loop stall |\n| --- | --- | --- | --- | --- |\n| 0.11.0 | 18.6 s | 60 | 120 | 8255 ms |\n| 0.11.1 | under 0.01 s | 0 | 0 | none measurable |\n\nIdle event-loop stall was 10.8 ms in both cases. On 0.11.1 the first request an instance receives warms both caches, and every request after that reaches the signature check without any outbound network call.\n\n## Credits\n\n@galanko, for reporting the issue and identifying both the missing caching and the blocking call.",
  "id": "GHSA-3g9q-v48f-hh9w",
  "modified": "2026-09-10T22:44:42Z",
  "published": "2026-09-10T22:44:42Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/security/advisories/GHSA-3g9q-v48f-hh9w"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-87011"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/commit/aeda6ff13a25d3b3ba1b303609f35382db22142c"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/open-webui/open-webui"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/releases/tag/v0.11.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Open WebUI: Unauthenticated requests can stall the server via uncached OIDC fetches in back-channel logout"
}

PYSEC-2026-4117

Vulnerability from pysec - Published: 2026-10-01 16:38 - Updated: 2026-10-01 17:10

Details

Summary

Preconditions

ENABLE_OAUTH_BACKCHANNEL_LOGOUT=true. The default is False, so a stock deployment is not affected. This setting is recommended in the Open WebUI hardening documentation, which is why the issue is treated as in scope.
At least one OIDC provider configured (OAUTH_CLIENT_ID, OAUTH_CLIENT_SECRET, OPENID_PROVIDER_URL).
No account, credential, session or secret identifier is required. The attacker needs network access to the instance and the configured issuer string, which is published in the provider's own discovery document.

Impact

No data is read, modified or exposed, and the forged token is still rejected. The cost is paid before the rejection.

Fix

Root cause

Proof of concept

20 sequential requests, provider answering immediately:

Version	Discovery fetches	Key-set fetches	Response
0.11.0	20	40	400
0.11.1	1	1	400

60 concurrent requests, provider answering in 150 ms:

Version	Wall time	Discovery fetches	Key-set fetches	Worst event-loop stall
0.11.0	18.6 s	60	120	8255 ms
0.11.1	under 0.01 s	0	0	none measurable

Credits

@galanko, for reporting the issue and identifying both the missing caching and the blocking call.

Severity

7.5 (High)


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

Impacted products

Name	purl
open-webui	pkg:pypi/open-webui

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "open-webui",
        "purl": "pkg:pypi/open-webui"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.9.0"
            },
            {
              "fixed": "0.11.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.10.0",
        "0.10.1",
        "0.10.2",
        "0.11.0",
        "0.9.0",
        "0.9.1",
        "0.9.2",
        "0.9.3",
        "0.9.4",
        "0.9.5",
        "0.9.6"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-87011",
    "GHSA-3g9q-v48f-hh9w"
  ],
  "details": "## Summary\n\nThe OIDC back-channel logout endpoint is unauthenticated by design, because the identity provider calls it without a browser session. Before checking whether the submitted logout token was genuine, the handler fetched the provider\u0027s discovery document and its signing keys over the network, and repeated both fetches on every request because nothing was cached. The signing-key fetch also ran as a blocking call inside the async event loop. A small number of requests carrying a worthless token was therefore enough to make the whole instance stop answering.\n\n## Preconditions\n\n- `ENABLE_OAUTH_BACKCHANNEL_LOGOUT=true`. The default is `False`, so a stock deployment is not affected. This setting is recommended in the Open WebUI hardening documentation, which is why the issue is treated as in scope.\n- At least one OIDC provider configured (`OAUTH_CLIENT_ID`, `OAUTH_CLIENT_SECRET`, `OPENID_PROVIDER_URL`).\n- No account, credential, session or secret identifier is required. The attacker needs network access to the instance and the configured issuer string, which is published in the provider\u0027s own discovery document.\n\n## Impact\n\nAgainst 0.11.0, with the identity provider answering in 150 ms, 60 concurrent requests carrying a token whose signature was four characters long stalled the async event loop for 8.3 seconds, measured against an idle baseline of 10.8 ms. For the length of that stall the process answers nothing: no chat requests, no API calls, no health check. Open WebUI runs a single worker by default, so the effect is instance-wide rather than per-connection, and no rate limit sits in front of the endpoint.\n\nThe same traffic is also amplified outward: 20 sequential requests produced 20 discovery fetches and 40 key-set fetches at the identity provider, so an attacker can drive load onto the provider through the instance.\n\nNo data is read, modified or exposed, and the forged token is still rejected. The cost is paid before the rejection.\n\n## Fix\n\nFixed in 0.11.1. The handler now resolves both the discovery document and the signing keys through the already-configured OAuth client, so each is fetched once per provider and reused afterwards, and both fetches are asynchronous rather than blocking the event loop. A token carrying no `kid` header is rejected before any key lookup happens. Upgrading is sufficient, and no configuration change is required.\n\n## Root cause\n\nAffected component: the OIDC back-channel logout handler in `backend/open_webui/utils/oauth.py`, reached through `POST /oauth/backchannel-logout`. Affected setups: releases 0.9.0 through 0.11.0 with back-channel logout enabled and an OIDC provider configured.\n\nThe handler treated its network work as cheap preparation rather than as work worth protecting. For every request it opened a new HTTP session per configured provider to re-read the discovery document, then constructed a fresh JWKS client, whose own cache consequently started empty each time, and asked that client for the signing key through a synchronous call issued directly on the event loop. All of this ran before the token signature was verified, so an attacker unable to produce a valid token still cost the server two network round trips and a blocked loop per request. Both fetches used the library default timeout of five minutes.\n\n## Proof of concept\n\nReproduced by running the unmodified handler from the 0.11.0 and 0.11.1 backends against a loopback identity provider that counted every inbound request and could answer with a configured delay. The submitted token carried a valid issuer and audience, a `kid` naming a key the provider does not hold, and `AAAA` as its signature.\n\n20 sequential requests, provider answering immediately:\n\n| Version | Discovery fetches | Key-set fetches | Response |\n| --- | --- | --- | --- |\n| 0.11.0 | 20 | 40 | 400 |\n| 0.11.1 | 1 | 1 | 400 |\n\n60 concurrent requests, provider answering in 150 ms:\n\n| Version | Wall time | Discovery fetches | Key-set fetches | Worst event-loop stall |\n| --- | --- | --- | --- | --- |\n| 0.11.0 | 18.6 s | 60 | 120 | 8255 ms |\n| 0.11.1 | under 0.01 s | 0 | 0 | none measurable |\n\nIdle event-loop stall was 10.8 ms in both cases. On 0.11.1 the first request an instance receives warms both caches, and every request after that reaches the signature check without any outbound network call.\n\n## Credits\n\n@galanko, for reporting the issue and identifying both the missing caching and the blocking call.",
  "id": "PYSEC-2026-4117",
  "modified": "2026-10-01T17:10:34.305219Z",
  "published": "2026-10-01T16:38:30.355680Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/security/advisories/GHSA-3g9q-v48f-hh9w"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-87011"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/commit/aeda6ff13a25d3b3ba1b303609f35382db22142c"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/open-webui/open-webui"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/releases/tag/v0.11.1"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/open-webui"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-3g9q-v48f-hh9w"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Open WebUI: Unauthenticated requests can stall the server via uncached OIDC fetches in back-channel logout"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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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.

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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Action not permitted

CVE-2026-87011 (GCVE-0-2026-87011)

BDU:2026-14479 (CVE-2026-87011)

FKIE_CVE-2026-87011

GHSA-3G9Q-V48F-HH9W

Summary

Preconditions

Impact

Fix

Root cause

Proof of concept

Credits

PYSEC-2026-4117

Summary

Preconditions

Impact

Fix

Root cause

Proof of concept

Credits

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