CVE-2024-4340: Sqlparse Denial of Service Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2m57-hf25-phgg",
  "modified" : "2024-05-01T11:09:12Z",
  "published" : "2024-04-15T20:21:25Z",
  "aliases" : [ "CVE-2024-4340" ],
  "summary" : "sqlparse parsing heavily nested list leads to Denial of Service",
  "details" : "### Summary\nPassing a heavily nested list to sqlparse.parse() leads to a Denial of Service due to RecursionError.\n\n### Details + PoC\nRunning the following code will raise Maximum recursion limit exceeded exception:\n```py\nimport sqlparse\nsqlparse.parse('[' * 10000 + ']' * 10000)\n```\nWe expect a traceback of RecursionError:\n```py\nTraceback (most recent call last):\n  File \"trigger_sqlparse_nested_list.py\", line 3, in <module>\n    sqlparse.parse('[' * 10000 + ']' * 10000)\n  File \"/home/uriya/.local/lib/python3.10/site-packages/sqlparse/__init__.py\", line 30, in parse\n    return tuple(parsestream(sql, encoding))\n  File \"/home/uriya/.local/lib/python3.10/site-packages/sqlparse/engine/filter_stack.py\", line 36, in run\n    stmt = grouping.group(stmt)\n  File \"/home/uriya/.local/lib/python3.10/site-packages/sqlparse/engine/grouping.py\", line 428, in group\n    func(stmt)\n  File \"/home/uriya/.local/lib/python3.10/site-packages/sqlparse/engine/grouping.py\", line 53, in group_brackets\n    _group_matching(tlist, sql.SquareBrackets)\n  File \"/home/uriya/.local/lib/python3.10/site-packages/sqlparse/engine/grouping.py\", line 48, in _group_matching\n    tlist.group_tokens(cls, open_idx, close_idx)\n  File \"/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py\", line 328, in group_tokens\n    grp = grp_cls(subtokens)\n  File \"/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py\", line 161, in __init__\n    super().__init__(None, str(self))\n  File \"/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py\", line 165, in __str__\n    return ''.join(token.value for token in self.flatten())\n  File \"/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py\", line 165, in <genexpr>\n    return ''.join(token.value for token in self.flatten())\n  File \"/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py\", line 214, in flatten\n    yield from token.flatten()\n  File \"/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py\", line 214, in flatten\n    yield from token.flatten()\n  File \"/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py\", line 214, in flatten\n    yield from token.flatten()\n  [Previous line repeated 983 more times]\nRecursionError: maximum recursion depth exceeded\n```\n\n### Fix suggestion\nThe [flatten()](https://github.com/andialbrecht/sqlparse/blob/master/sqlparse/sql.py#L207) function of TokenList class should limit the recursion to a maximal depth:\n```py\nfrom sqlparse.exceptions import SQLParseError\n\nMAX_DEPTH = 100\n\n    def flatten(self, depth=1):\n        \"\"\"Generator yielding ungrouped tokens.\n\n        This method is recursively called for all child tokens.\n        \"\"\"\n    if depth >= MAX_DEPTH:\n        raise SQLParseError('Maximal depth reached')\n        for token in self.tokens:\n            if token.is_group:\n                yield from token.flatten(depth + 1)\n            else:\n                yield token\n```\n\n### Impact\nDenial of Service (the impact depends on the use).\nAnyone parsing a user input with sqlparse.parse() is affected.\n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "sqlparse"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.5.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/andialbrecht/sqlparse/security/advisories/GHSA-2m57-hf25-phgg"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2024-4340"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/andialbrecht/sqlparse/commit/b4a39d9850969b4e1d6940d32094ee0b42a2cf03"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/andialbrecht/sqlparse"
  }, {
    "type" : "WEB",
    "url" : "https://research.jfrog.com/vulnerabilities/sqlparse-stack-exhaustion-dos-jfsa-2024-001031292"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-674" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-04-15T20:21:25Z",
    "nvd_published_at" : null
  }
}