Python Liquid: Infinite loop when parsing malformed `{% case %}` tags

{
  "id": "14117e5850fe14e7c1a0b3d6e1d239eb4ca9f9abbe98f57eb11c2091906e557e",
  "url": "https://osv.dev/vulnerability/CVE-2026-55865",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Python Liquid: Infinite loop when parsing malformed `{% case %}` tags",
    "summary": "Python Liquid is a Python engine for the Liquid template language. Prior to 2.2.1, given a malformed {% case %} tag without an associated {% when %} or {% else %} block and no terminating {% endcase %} tag, Python Liquid hangs in an infinite loop at parse time because liquid.TokenStream.eof did not give the EOF token matching kind and value fields, allowing malicious template authors to craft templates for a denial of service attack. This issue is fixed in version 2.2.1.",
    "evidence": "osv:CVE-2026-55865",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-55865",
      "aliases": [
        "CVE-2026-55865",
        "GHSA-vq2f-vcc9-j8mv",
        "PYSEC-2026-3035"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/jg-rp/liquid",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "1b915914fdb154a0dfbffbfa796c520a6e8de905"
                },
                {
                  "fixed": "26db8931cf35e8433c1ca506fc32c3bb62f743d4"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "2.2.1"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "26db8931cf35e8433c1ca506fc32c3bb62f743d4"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "1b915914fdb154a0dfbffbfa796c520a6e8de905"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v2.2.1"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v2.2.0",
            "v2.1.0",
            "v2.0.2",
            "v2.0.1",
            "v2.0.0",
            "v1.13.0",
            "v1.12.2",
            "v1.12.1",
            "v1.12.0",
            "v1.11.0",
            "v1.10.2",
            "v1.10.0",
            "v1.9.4",
            "v1.9.3",
            "v1.9.2",
            "v1.9.1",
            "v1.9.0",
            "v1.8.1",
            "v1.8.0",
            "v1.7.0",
            "v1.6.1",
            "v1.6.0",
            "v1.5.1",
            "v1.5.0",
            "v1.4.7",
            "v1.4.6",
            "v1.4.5",
            "v1.4.3",
            "v1.4.0",
            "v1.3.0",
            "v1.2.0",
            "v1.1.7",
            "v1.1.5",
            "v1.1.3",
            "v1.1.0",
            "v1.0.0",
            "v0.9.0",
            "v0.8.0",
            "v0.7.7",
            "v0.7.2",
            "v0.6.2"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55865.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:52.947497285Z",
      "provider": "osv",
      "references": [
        "https://github.com/jg-rp/liquid/releases/tag/v2.2.1",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55865.json",
        "https://github.com/jg-rp/liquid/security/advisories/GHSA-vq2f-vcc9-j8mv",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-55865",
        "https://github.com/jg-rp/liquid/commit/26db8931cf35e8433c1ca506fc32c3bb62f743d4"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-835"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55865.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-55865",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 521854,
  "published_at": "2026-07-09T20:34:38.618+00:00"
}