CVE-2026-62296 hapifhir CVE debrief

Who should care

Defenders responsible for HAPI FHIR implementations, particularly those using versions prior to 6.9.11, should assess their exposure and take steps to prevent the submission of malicious FHIR resources.

Why it matters

CVE-2026-62296 is a vulnerability in HAPI FHIR that can be exploited to crash parsing or validation worker threads, affecting validator services and applications that parse FHIR resources. Defenders should prioritize updating to version 6.9.11 or later and validate and sanitize FHIR resources to prevent the submission of malicious narratives.

• Crash of parsing or validation worker threads
• Denial of service for validator services and applications parsing FHIR resources

Technical summary

The XhtmlParser.java file in HAPI FHIR does not impose a maximum element nesting depth, allowing a deeply nested text.div narrative to trigger unbounded recursion between parseElementInner() and parseElement(), resulting in a StackOverflowError. This vulnerability affects validator services and any application that parses attacker-supplied FHIR JSON or XML. Defenders should prioritize updating to version 6.9.11 or later and validate and sanitize FHIR resources to prevent the submission of malicious narratives. The fix involves updating the XhtmlParser.java file to impose a maximum element nesting depth.

Defensive priority

Defenders should prioritize updating to version 6.9.11 or later to prevent this vulnerability. They should also validate and sanitize FHIR resources to prevent the submission of malicious narratives.

Recommended defensive actions

• Update to version 6.9.11 or later
• Validate and sanitize FHIR resources
• Monitor for suspicious FHIR resource submissions
• Review compensating controls for exposed systems
• Check relevant monitoring, detection, and logs for exposed assets
• Track exceptions, retest remediated assets
• Confirm whether affected product deployments exist in managed environments

Evidence notes

The CVE record and NVD entry provide information about the vulnerability, its impact, and the fix. However, the exact scope of affected systems and the number of potential victims are not specified. To verify, defenders should review the official CVE record and NVD entry for source-provided metadata and vulnerability assessments. Limited source detail suggests that defenders should proceed with caution and validate FHIR resources to prevent malicious narratives.

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.