datamodel-code-generator vulnerable to SSRF protection bypass via DNS rebinding

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N

EPSS

• CVE-2026-55391: 0.30% estimated exploitation activity in the next 30 days; percentile 23.35 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary datamodel-code-generator's anti-SSRF guard validates the resolved IP of a fetch target once and then lets httpx perform its own independent DNS resolution to connect, so the validated address is never pinned. A hostname that resolves to a public IP at validation time and a private IP at connection time (DNS rebinding) bypasses the guard and reaches loopback, link-local cloud-metadata endpoints (169.254.169.254), and other internal services — even with the default allowprivatenetwork=False. This is a server-side request forgery reachable when the tool fetches an attacker-influenced URL (remote $ref, or --url). Details In src/datamodelcodegenerator/http.py, getbody() calls validateurlforfetch(), which resolves the host via getipsfromhost() (socket.getaddrinfo) and rejects non-global addresses: It then connects with a separate, independent resolution: Nothing ties the connection to the IP that passed validation. Between the two resolutions a low-TTL attacker-controlled record…

Published by the source

28 Jul 2026, 21:45 UTC

Last modified by the source

28 Jul 2026, 21:45 UTC

Source last checked

26 Oct 2026, 13:50 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-vx7x-vcc2-c44g

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# Patch Next advisory brief: CVE-2026-55391

Advisory: datamodel-code-generator vulnerable to SSRF protection bypass via DNS rebinding
IDs: CVE-2026-55391, GHSA-vx7x-vcc2-c44g
Record: https://patchnext.com/advisories/cve-2026-55391 (revision 1, source checked 26 Oct 2026, 13:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: datamodel-code-generator 0.63.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI datamodel-code-generator: affected <= 0.62.0; fixed in 0.63.0

## Suggested inspection (read-only)
- `python -m pip show datamodel-code-generator`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on datamodel-code-generator.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-vx7x-vcc2-c44g (GitHub-reviewed advisory GHSA-vx7x-vcc2-c44g lists affected ranges: PyPI datamodel-code-generator >=0 <=0.62.0)

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