CVE-2026-104020 Uncontrolled recursion in the Ion reader in Amazon Ion Python
A remote attacker can crash applications using the Amazon Ion Python library by sending deeply nested Ion values, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-104020?
CVE-2026-104020 is a high-severity denial of service vulnerability in Amazon ion-python, published on 1 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-674
Which versions are affected by CVE-2026-104020?
How do I fix CVE-2026-104020?
No fix has been published for CVE-2026-104020 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-104020 being exploited?
There is no known exploitation of CVE-2026-104020 in the wild and no public exploit code.
Sources
Also known as GHSA-93q6-f8hx-vv7f.