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{"schema_version":"1.9.0","id":"GHSA-954p-556p-r752","published":"2026-07-28T21:42:22Z","modified":"2026-09-10T03:51:11.259728609Z","aliases":["CVE-2026-54690","PYSEC-2026-3560"],"summary":"datamodel-code-generator vulnerable to SSRF via JSON-Schema `$ref` to HTTP URL (silent by default)","details":"### Summary\n\nJSON-Schema `$ref` values pointing at HTTP or HTTPS URLs are silently dereferenced by `datamodel-code-generator` with no IP/host validation, no scheme allow-list, and redirects followed unconditionally. The `--allow-remote-refs` gate added in 0.56.0 defaults to `None`, which only emits a deprecation warning and then fetches the URL anyway; only explicit `--allow-remote-refs=false` blocks the request. The fetched body is parsed as a sub-schema and reflected verbatim into the generated `.py` source. As a result, any JSON-Schema document the developer feeds to `datamodel-codegen` — including documents authored by an attacker — can pivot to arbitrary internal addresses and leak the response into the generated code, with no developer cooperation beyond running the tool.\n\n### Details\n\nSink: `src/datamodel_code_generator/parser/jsonschema.py`, `_get_ref_body` (lines 4776–4793, at tag `0.60.1` / commit `a321547e`):\n\n```python\ndef _get_ref_body(self, resolved_ref: str) -> dict[str, YamlValue]:\n if is_url(resolved_ref):\n if not resolved_ref.startswith(\"file://\") and self.http_local_ref_path is None:\n if self.allow_remote_refs is False:\n raise Error(f\"Fetching remote $ref is disabled: {resolved_ref}...\")\n if self.allow_remote_refs is None:\n warn_deprecated( # (A) warn only\n \"behavior.remote-ref-default\",\n details=f\"Reference: {resolved_ref}\",\n stacklevel=2,\n )\n return self._get_ref_body_from_url(resolved_ref) # (B) fetch fires\n return self._get_ref_body_from_remote(resolved_ref)\n```\n\n- (A) emits a deprecation warning when `allow_remote_refs` is its default (`None`); execution falls through to (B).\n- (B) routes the URL through `_get_text_from_url` → `get_body`, the same fetcher described in other report — no IP validation, redirects followed.\n\nThe fetched body is then parsed as a sub-schema and merged into the model graph, so `description`, `title`, `properties`, etc. from the remote document end up in the generated `.py` source.\n\nOnly affects users who installed the `[http]` extra (`pip install 'datamodel-code-generator[http]'`).\n\n### PoC\n\nA self-contained one-file PoC is available here: https://gist.github.com/thegr1ffyn/562a6972d7dc3f2869458ae93fc608c0\n\n### Impact\n\n**Who is impacted.** Anyone running `datamodel-codegen` on a JSON-Schema or OpenAPI document of uncertain provenance, with the `[http]` extra installed. Real-world scenarios:\n\n1. **Trojaned OpenAPI document.** A public REST API publishes `openapi.yaml`. One `$ref` points at `http://169.254.169.254/latest/meta-data/iam/security-credentials/<role>`; running `datamodel-codegen` against the spec from an EC2 instance leaks the IAM credentials into the generated client.\n2. **Customer-supplied JSON Schema.** A B2B SaaS auto-generates client code from customer-uploaded schemas. The customer adds an HTTP `$ref` to `http://internal-admin:8080/users.json`; the response (e.g. JSON user list) ends up in the generated Python the SaaS hands back to the customer.\n3. **CI on a private network.** A PR adds `schemas/inbound.json` with an HTTP `$ref` pointed at a service reachable only from the CI cluster's VPC; the CI runner fetches it and the generated `.py` leaks the response in PR artifacts.\n\nHigher real-world risk than the sibling CLI-flag SSRF (other SSRF in this report bundle) because the *schema author* chooses the destination — the developer doesn't have to type any URL.\n\n**Suggested fix.**\n\n1. Flip the default in `parser/base.py`: `allow_remote_refs: bool = False`, and remove the silent-fetch-with-warning fallback at `parser/jsonschema.py:4786-4791`.\n2. When fetching is allowed, apply the same IP/host validation proposed for other submitted SSRF report to both the initial `$ref` URL and every redirect target.\n3. Document HTTP `$ref` in a third-party schema as equivalent to running `curl` on the developer's host.\n\n### Maintainer resolution\n\nThis `$ref` report is fixed by the same shared HTTP fetcher hardening that resolved GHSA-rfr2-mq9m-x2qx. The code landed through the GHSA-rfr2 private security PR koxudaxi/datamodel-code-generator-ghsa-rfr2-mq9m-x2qx#1 and was merged into the public repository as 5fdba4a09f2d7a9996a504975b7ef7d63e3715bb. Follow-up generated-file and coverage fixes were merged in koxudaxi/datamodel-code-generator#3279 and docs were synced in #3280. The patched release is 0.61.0.\n\nNo separate net code diff remains in the GHSA-954 private PR because the shared HTTP fetcher patch is already present on `main`. This advisory remains separate because the affected entry point is remote JSON Schema/OpenAPI `$ref` resolution rather than direct CLI `--url` input.\n\nThe fix does not flip the `--allow-remote-refs` compatibility default in this patch. Instead, it mitigates the SSRF issue by blocking localhost, loopback, private, link-local, reserved, and other non-public network targets by default, validating every redirect target before it is fetched, and requiring `--allow-private-network` / `allow_private_network=True` for trusted internal schema endpoints. Remote `$ref` fetching remains controlled by `--allow-remote-refs`; non-public/internal targets additionally require `--allow-private-network`.\n\nSubmitted by: Hamza Haroon (thegr1ffyn)","affected":[{"package":{"name":"datamodel-code-generator","ecosystem":"PyPI","purl":"pkg:pypi/datamodel-code-generator"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.9.1"},{"fixed":"0.61.0"}]}],"versions":["0.10.0","0.10.1","0.10.2","0.10.3","0.11.0","0.11.1","0.11.10","0.11.11","0.11.12","0.11.13","0.11.14","0.11.15","0.11.16","0.11.17","0.11.18","0.11.19","0.11.2","0.11.20","0.11.3","0.11.4","0.11.5","0.11.6","0.11.7","0.11.8","0.11.9","0.12.0","0.12.1","0.12.2","0.12.3","0.13.0","0.13.1","0.13.2","0.13.3","0.13.4","0.13.5","0.14.0","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","0.60.2","0.9.1","0.9.2","0.9.3","0.9.4"],"database_specific":{"last_known_affected_version_range":"<= 0.60.2","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-954p-556p-r752/GHSA-954p-556p-r752.json"}}],"references":[{"type":"WEB","url":"https://github.com/koxudaxi/datamodel-code-generator/security/advisories/GHSA-954p-556p-r752"},{"type":"WEB","url":"https://github.com/koxudaxi/datamodel-code-generator/commit/5fdba4a09f2d7a9996a504975b7ef7d63e3715bb"},{"type":"PACKAGE","url":"https://github.com/koxudaxi/datamodel-code-generator"},{"type":"WEB","url":"https://github.com/koxudaxi/datamodel-code-generator/releases/tag/0.61.0"}],"database_specific":{"cwe_ids":["CWE-918"],"github_reviewed":true,"github_reviewed_at":"2026-07-28T21:42:22Z","nvd_published_at":null,"severity":"HIGH"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N"}]} |