CVE-2026-55470
Description
A flaw was found in HAPI FHIR, a Java implementation of the HL7 FHIR standard. The fix for a previous vulnerability (CVE-2026-45367) was incomplete in the DSTU2 module. Specifically, the FHIRPathEngine.matches() function in org.hl7.fhir.dstu2 did not include protection against regular expression timeouts. This allows an unauthenticated attacker to submit a specially crafted FHIRPath expression, triggering catastrophic regular expression (regex) backtracking. The consequence is a Regular Expression Denial of Service (ReDoS), which can exhaust server CPU resources and lead to service disruption.
Statement
This flaw is rated as Important because an unauthenticated, remote attacker can exploit an incomplete patch in the HAPI FHIR DSTU2 module. By submitting a specially crafted FHIRPath expression, an attacker can trigger a Regular Expression Denial of Service (ReDoS) attack, leading to significant resource exhaustion and service unavailability on affected systems.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU)
Attackers can create crafted inputs that intentionally cause the regular expression to use excessive backtracking in a way that causes the CPU consumption to spike.
Frequently Asked Questions
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