# CVE-2026-104020: Uncontrolled recursion in the Ion reader in Amazon Ion Python

> CVE-2026-104020: Uncontrolled recursion in the Ion reader in Amazon Ion Python. CVSS 7.5 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-104020
Last updated: 2026-10-09T16:36:02Z

- Published: 2026-10-01 20:36 UTC · Updated: 2026-10-09 16:36 UTC · Assigner: AMZN
- CVSS: 7.5 (CVSS 3.1) · Severity: High · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS: 0.44%, 38th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-674

## Description

Uncontrolled recursion in the Ion reader in Amazon Ion Python before 0.15.0 might allow a remote unauthenticated actor to crash the application using the library, resulting in a denial of service, via a crafted, deeply nested Ion value. To remediate this issue, users should upgrade to version 0.15.0 or later.

## Affected vendors and products

- Amazon: ion-python

## Tracked companies

- [Amazon Web Services](https://rewindex.com/company/aws.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-104020)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-104020)
- [https://aws.amazon.com/security/security-bulletins/2026-122-aws/](https://aws.amazon.com/security/security-bulletins/2026-122-aws/)
- [https://github.com/amazon-ion/ion-python/releases/tag/v0.15.0](https://github.com/amazon-ion/ion-python/releases/tag/v0.15.0)
- [https://github.com/amazon-ion/ion-python/security/advisories/GHSA-93q6-f8hx-vv7f](https://github.com/amazon-ion/ion-python/security/advisories/GHSA-93q6-f8hx-vv7f)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-104020 · Markdown: https://rewindex.com/cve/CVE-2026-104020.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-104020 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T03:13:15.086Z