Open WebUI: ReDoS in skill-mention regexes causes whole-instance DoS on default config

{
  "id": "a339c168e469733b596b65fd216bcc16cedc51a443b3cf581046e47f2ec81e18",
  "url": "https://osv.dev/vulnerability/CVE-2026-59220",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Open WebUI: ReDoS in skill-mention regexes causes whole-instance DoS on default config",
    "summary": "Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.9.2 before 0.10.0, the SKILL_MENTION_RE and strip_re regular expressions in backend/open_webui/utils/middleware.py parsed <$skillId|label> skill mentions with overlapping quantifiers, allowing an authenticated chat message containing <$ without a closing > to trigger quadratic backtracking and block the asyncio event loop. This issue is fixed in version 0.10.0.",
    "evidence": "osv:CVE-2026-59220",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-59220",
      "aliases": [
        "CVE-2026-59220",
        "GHSA-ffpj-xv5c-p3gw",
        "PYSEC-2026-3596"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/open-webui/open-webui",
              "type": "GIT",
              "events": [
                {
                  "introduced": "8dae237a0bfdac4b7f55b463b3e2769ea4b94a0b"
                },
                {
                  "fixed": "4d2e13cf2bcc451b33bb6374bea4d2163e6cc94c"
                },
                {
                  "fixed": "61a26722155ec6ee1b629cf8dfcf975098c18331"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:openwebui:open_webui:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0.9.2"
                      },
                      {
                        "fixed": "0.10.0"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "61a26722155ec6ee1b629cf8dfcf975098c18331"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "4d2e13cf2bcc451b33bb6374bea4d2163e6cc94c"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v0.10.0"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v0.9.5",
            "v0.9.4",
            "v0.9.3",
            "v0.9.2"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-59220.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:35.838819635Z",
      "provider": "osv",
      "references": [
        "https://github.com/open-webui/open-webui/releases/tag/v0.10.0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59220.json",
        "https://github.com/open-webui/open-webui/security/advisories/GHSA-ffpj-xv5c-p3gw",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-59220",
        "https://github.com/open-webui/open-webui/commit/61a26722155ec6ee1b629cf8dfcf975098c18331"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-1333"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59220.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-59220",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 503221,
  "published_at": "2026-07-09T16:09:41.127+00:00"
}