PYSEC-2026-3566

Vulnerability from pysec - Published: 2026-08-04 11:34 - Updated: 2026-08-04 13:36
VLAI
Details

Summary

datamodel-code-generator is vulnerable to code injection when a developer passes an --extra-template-data file whose comment value contains a literal \r (carriage return). The comment variable is rendered into a Python # comment in six built-in templates with no line-terminator escaping. Python's tokenizer treats a bare CR as a physical-line terminator (see Python language reference — Physical lines), so the comment ends at the \r and the text after it is parsed as Python, including, when the CR is followed by suitable indentation, as a statement within the class body that follows on the next template line.

Details

The vulnerable templates each contain # {{ comment }} with no escaping:

  • src/datamodel_code_generator/model/template/TypeAliasAnnotation.jinja2:12 and :19
  • src/datamodel_code_generator/model/template/TypeAliasType.jinja2:12 and :19
  • src/datamodel_code_generator/model/template/TypeStatement.jinja2:12 and :19
  • src/datamodel_code_generator/model/template/pydantic_v2/BaseModel.jinja2:4
  • src/datamodel_code_generator/model/template/pydantic_v2/RootModel.jinja2:19
  • src/datamodel_code_generator/model/template/pydantic_v2/RootModelTypeAlias.jinja2:13

The pydantic_v2/BaseModel.jinja2:4 site is representative:

class {{ class_name }}({{ base_class }}):{% if comment is defined %}  # {{ comment }}{% endif %}

When the developer-supplied extras file populates comment for a model, the value reaches the template via DataModel.extra_template_data (set in src/datamodel_code_generator/model/base.py:736-742) and Jinja2 interpolates it raw. None of the templates use comment_safe, escape_docstring, or any other line-terminator filter.

PoC

Complete self contained POC is available at my secret gist: https://gist.github.com/thegr1ffyn/8ad6b8cb3cc2be9d3a0144aeb6896a3f

Impact

  • Who's affected: any developer or CI pipeline that runs datamodel-codegen --extra-template-data <file> where the extras file is influenced by attacker-controlled input. Realistic scenarios include:
  • Extras file generated from a third-party schema-annotation system.
  • Extras file vendored from an upstream repository.
  • Extras file produced by a script that merges multiple comment sources.
  • Build pipelines that template the extras file from environment variables, ticket descriptions, or commit metadata.
  • What it gains: arbitrary Python code execution in the importer's process at import time.
  • What it does NOT need: the schema itself can be entirely benign; only the extras file needs to contain the malicious comment.
  • What does block it: not passing --extra-template-data, or rejecting extras files whose comment values contain \r, \x0b, or \x0c before invocation.

Resolution

The fix normalizes comment values from built-in --extra-template-data before template rendering. Inline comments now convert CRLF, bare CR, vertical tab, and form feed into LF and prefix continuation lines with #, so attacker-controlled text stays inside the generated Python comment block.

Remediation

Upgrade to datamodel-code-generator 0.60.2 or later.

This issue affects datamodel-code-generator versions >= 0.14.1, <= 0.60.1 and is fixed in 0.60.2.

Submitted by: Hamza Haroon (thegr1ffyn)

Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Impacted products
Name purl
datamodel-code-generator pkg:pypi/datamodel-code-generator
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "datamodel-code-generator",
        "purl": "pkg:pypi/datamodel-code-generator"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.14.1"
            },
            {
              "fixed": "0.60.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.14.1",
        "0.15.0",
        "0.16.0",
        "0.16.1",
        "0.17.0",
        "0.17.1",
        "0.17.2",
        "0.18.0",
        "0.18.1",
        "0.19.0",
        "0.20.0",
        "0.21.0",
        "0.21.1",
        "0.21.2",
        "0.21.3",
        "0.21.4",
        "0.21.5",
        "0.22.0",
        "0.22.1",
        "0.23.0",
        "0.24.0",
        "0.24.1",
        "0.24.2",
        "0.25.0",
        "0.25.1",
        "0.25.2",
        "0.25.3",
        "0.25.4",
        "0.25.5",
        "0.25.6",
        "0.25.7",
        "0.25.8",
        "0.25.9",
        "0.26.0",
        "0.26.1",
        "0.26.2",
        "0.26.3",
        "0.26.4",
        "0.26.5",
        "0.27.0",
        "0.27.1",
        "0.27.2",
        "0.27.3",
        "0.28.0",
        "0.28.1",
        "0.28.2",
        "0.28.3",
        "0.28.4",
        "0.28.5",
        "0.29.0",
        "0.30.0",
        "0.30.1",
        "0.30.2",
        "0.31.0",
        "0.31.1",
        "0.31.2",
        "0.32.0",
        "0.33.0",
        "0.34.0",
        "0.35.0",
        "0.36.0",
        "0.37.0",
        "0.38.0",
        "0.39.0",
        "0.40.0",
        "0.41.0",
        "0.42.0",
        "0.42.1",
        "0.42.2",
        "0.43.0",
        "0.43.1",
        "0.44.0",
        "0.45.0",
        "0.46.0",
        "0.47.0",
        "0.48.0",
        "0.49.0",
        "0.50.0",
        "0.51.0",
        "0.52.0",
        "0.52.1",
        "0.52.2",
        "0.53.0",
        "0.54.0",
        "0.54.1",
        "0.55.0",
        "0.56.0",
        "0.56.1",
        "0.57.0",
        "0.58.0",
        "0.59.0",
        "0.59.1",
        "0.60.0",
        "0.60.1"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-54654",
    "GHSA-wjv6-jcfj-mf9r"
  ],
  "details": "### Summary\n\n`datamodel-code-generator` is vulnerable to code injection when a developer passes an `--extra-template-data` file whose `comment` value contains a literal `\\r` (carriage return). The `comment` variable is rendered into a Python `#` comment in six built-in templates with **no** line-terminator escaping. Python\u0027s tokenizer treats a bare CR as a physical-line terminator (see [Python language reference \u2014 Physical lines](https://docs.python.org/3/reference/lexical_analysis.html#physical-lines)), so the comment ends at the `\\r` and the text after it is parsed as Python, including, when the CR is followed by suitable indentation, as a statement within the class body that follows on the next template line.\n\n### Details\n\nThe vulnerable templates each contain `# {{ comment }}` with no escaping:\n\n- `src/datamodel_code_generator/model/template/TypeAliasAnnotation.jinja2:12` and `:19`\n- `src/datamodel_code_generator/model/template/TypeAliasType.jinja2:12` and `:19`\n- `src/datamodel_code_generator/model/template/TypeStatement.jinja2:12` and `:19`\n- `src/datamodel_code_generator/model/template/pydantic_v2/BaseModel.jinja2:4`\n- `src/datamodel_code_generator/model/template/pydantic_v2/RootModel.jinja2:19`\n- `src/datamodel_code_generator/model/template/pydantic_v2/RootModelTypeAlias.jinja2:13`\n\nThe `pydantic_v2/BaseModel.jinja2:4` site is representative:\n\n```jinja2\nclass {{ class_name }}({{ base_class }}):{% if comment is defined %}  # {{ comment }}{% endif %}\n```\n\nWhen the developer-supplied extras file populates `comment` for a model, the value reaches the template via `DataModel.extra_template_data` (set in `src/datamodel_code_generator/model/base.py:736-742`) and Jinja2 interpolates it raw. None of the templates use `comment_safe`, `escape_docstring`, or any other line-terminator filter.\n\n### PoC\nComplete self contained POC is available at my secret gist: https://gist.github.com/thegr1ffyn/8ad6b8cb3cc2be9d3a0144aeb6896a3f\n\n### Impact\n\n- **Who\u0027s affected**: any developer or CI pipeline that runs `datamodel-codegen --extra-template-data \u003cfile\u003e` where the extras file is influenced by attacker-controlled input. Realistic scenarios include:\n  - Extras file generated from a third-party schema-annotation system.\n  - Extras file vendored from an upstream repository.\n  - Extras file produced by a script that merges multiple `comment` sources.\n  - Build pipelines that template the extras file from environment variables, ticket descriptions, or commit metadata.\n- **What it gains**: arbitrary Python code execution in the importer\u0027s process at `import` time.\n- **What it does NOT need**: the schema itself can be entirely benign; only the extras file needs to contain the malicious `comment`.\n- **What does block it**: not passing `--extra-template-data`, or rejecting extras files whose `comment` values contain `\\r`, `\\x0b`, or `\\x0c` before invocation.\n\n### Resolution\n\nThe fix normalizes `comment` values from built-in `--extra-template-data` before template rendering. Inline comments now convert CRLF, bare CR, vertical tab, and form feed into LF and prefix continuation lines with `# `, so attacker-controlled text stays inside the generated Python comment block.\n\n### Remediation\n\nUpgrade to `datamodel-code-generator` `0.60.2` or later.\n\nThis issue affects `datamodel-code-generator` versions `\u003e= 0.14.1, \u003c= 0.60.1` and is fixed in `0.60.2`.\n\nSubmitted by: Hamza Haroon (thegr1ffyn)",
  "id": "PYSEC-2026-3566",
  "modified": "2026-08-04T13:36:16.259383Z",
  "published": "2026-08-04T11:34:44.771231Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/koxudaxi/datamodel-code-generator/security/advisories/GHSA-wjv6-jcfj-mf9r"
    },
    {
      "type": "WEB",
      "url": "https://github.com/koxudaxi/datamodel-code-generator/commit/b73abb5cd703a50471b8950bbd3bd0b82ad71de7"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/koxudaxi/datamodel-code-generator"
    },
    {
      "type": "WEB",
      "url": "https://github.com/koxudaxi/datamodel-code-generator/releases/tag/0.60.2"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/datamodel-code-generator"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-wjv6-jcfj-mf9r"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54654"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "`datamodel-code-generator` vulnerable to code injection via unescaped carriage return in `--extra-template-data` `comment` field"
}



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