CVE-2026-62295 hapifhir CVE debrief

Who should care

Defenders responsible for healthcare interoperability systems using HAPI FHIR should assess exposure and prioritize upgrading to version 6.9.11 or later to prevent potential denial-of-service attacks.

Why it matters

CVE-2026-62295 is a denial-of-service vulnerability in HAPI FHIR that can be triggered by a deeply nested, syntactically valid FHIR JSON document. Defenders should prioritize upgrading to version 6.9.11 or later and assess exposure in their systems.

• Denial-of-service attacks can cause worker loss or process instability
• Potential for system crashes or instability
• Need for input validation and error handling for FHIR JSON documents

Technical summary

The JSON utility parser in org.hl7.fhir.utilities.json.parser.JsonParser does not enforce a maximum nesting depth for arrays or objects. This allows a small but deeply nested, syntactically valid FHIR JSON document to trigger unbounded readArray() or readObject() recursion, raising a StackOverflowError before structural validation runs. An attacker who can submit JSON resources for validation can thus crash the request thread, and services that do not isolate StackOverflowError safely may experience worker loss or process instability — a denial-of-service condition. This issue is fixed in version 6.9.11. Defenders should prioritize upgrading to version 6.9.11 or later to prevent potential denial-of-service

Defensive priority

Defenders should prioritize upgrading to version 6.9.11 or later to prevent potential denial-of-service attacks. They should also assess exposure in their systems, particularly those using HAPI FHIR for healthcare interoperability.

Recommended defensive actions

• Upgrade to version 6.9.11 or later
• Assess exposure in systems using HAPI FHIR
• Implement input validation and error handling for FHIR JSON documents
• 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
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The vulnerability is caused by the JSON utility parser in org.hl7.fhir.utilities.json.parser.JsonParser not enforcing a maximum nesting depth for arrays or objects. This allows a small but deeply nested FHIR JSON document to trigger unbounded recursion, leading to a StackOverflowError.

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.