CVE-2026-84851: Uncontrolled recursion in the Ion reader in Amazon Ion-C before 1.1.6

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-03 · updated 2026-09-03
Weakness: CWE-674

Description

An uncontrolled recursion issue exists in Amazon Ion-C versions before 1.1.6 that might allow a remote unauthenticated actor to craft Ion data that exhausts the native call stack and crashes the application using the library, resulting in a denial of service.

Affected products

Amazon ion-c: before 1.1.6 — fixed in 1.1.6

How to fix

Upgrade to a fixed version: Amazon ion-c 1.1.6. Check the vendor advisory for mitigations.

References

https://aws.amazon.com/security/security-bulletins/2026-094-aws/
https://github.com/amazon-ion/ion-c/releases/tag/v1.1.6
https://github.com/amazon-ion/ion-c/security/advisories/GHSA-9gfg-hgj4-gh44

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