What is CVE-2026-104020?

CVE-2026-104020 is a high-severity vulnerability in Amazon Ion-Python, classified under Uncontrolled Recursion. CVSS score: 7.5/10. Published 2026-10-01.

How severe is CVE-2026-104020?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Amazon Ion-Python

CVE-2026-104020

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.

Published 2026-10-01 · last modified 2026-10-02.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Amazon Ion-Python

Weakness classification (CWE)

CWE-674 — Uncontrolled Recursion

References

ff89ba41-3aa1-4d27-914a-91399e9639e5 (patch)
ff89ba41-3aa1-4d27-914a-91399e9639e5 (vendor-advisory)
ff89ba41-3aa1-4d27-914a-91399e9639e5 (third-party-advisory)

Frequently asked questions

What is CVE-2026-104020?: CVE-2026-104020 is a high-severity vulnerability in Amazon Ion-Python, classified under Uncontrolled Recursion. CVSS score: 7.5/10. Published 2026-10-01.
How severe is CVE-2026-104020?: High severity. CVSS v3 base score is 7.5 out of 10.