High severity · published Oct 1, 2026
CVE-2026-104020
Uncontrolled recursion in the Ion reader in Amazon Ion Python
7.5
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 38% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
IO
ion-python · Amazon
before 0.15.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-104020
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-104020
patch
https://github.com/amazon-ion/ion-python/releases/tag/v0.15.0
vendor-advisory
https://aws.amazon.com/security/security-bulletins/2026-122-aws/
third-party-advisory
https://github.com/amazon-ion/ion-python/security/advisories/GHSA-93q6-f8hx-vv7f