CVE-2026-104020 Amazon CVE debrief

Who should care

Defenders and developers using the Amazon Ion Python library should assess exposure and prioritize remediation to prevent potential denial of service attacks. They should review the vendor advisory, assess affected systems, and verify potential impacts. Security teams and vulnerability management teams should also review the vulnerability and prioritize remediation efforts.

Why it matters

CVE-2026-104020 is a high-severity vulnerability in the Amazon Ion Python library that could lead to denial of service attacks. Defenders and developers should assess exposure and prioritize remediation to prevent potential impacts.

• Denial of service attacks could impact application availability
• Remediation requires upgrading to version 0.15.0 or later
• Verification of affected systems and potential consequences is necessary

Technical summary

The Amazon Ion Python library before version 0.15.0 is vulnerable to uncontrolled recursion in the Ion reader, which could allow a remote unauthenticated actor to crash the application using the library, resulting in a denial of service. The vulnerability is caused by a deeply nested Ion value that can trigger excessive recursion. To remediate this issue, users should upgrade to version 0.15.0 or later and review affected systems for potential exposure. The CVE record and source item provide information about the vulnerability, its impact, and the remediation steps.

Defensive priority

Upgrade to version 0.15.0 or later to prevent denial of service attacks

Recommended defensive actions

• Upgrade to version 0.15.0 or later
• Review and update affected systems
• Monitor for potential denial of service attacks
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record and source item provide information about the vulnerability, its impact, and the remediation steps. However, the exact scope of affected systems and potential consequences require verification from the supplied official sources. Defenders should verify the affected systems, review the vendor advisory, and assess potential impacts.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.