CVE-2026-45367 is a high-severity inefficient regular expression (ReDoS) vulnerability in ca.uhn.hapi.fhir:org.hl7.fhir.dstu2 (maven), affecting versions <= 6.9.6. It is fixed in 6.9.7.
Summary All implementations of FHIRPathEngine accept arbitrary FHIRPath expressions and evaluate them without input validation. The FHIRPath functions matches(), matchesFull(), and replaceMatches() pass user-controlled regular expressions directly to Java's Pattern.compile() and String.replaceAll() without complexity checks or timeouts. An attacker can send a resource containing an evil regex pattern that causes catastrophic backtracking, exhausting system resources, and causing Denial-of-Service. Details The vulnerability exists in regex execution in FHIRPathEngine implementations across multiple code modules. For example the org.hl7.fhir.r5 module: Entry point 1, FHIRPathEngine.java:5929 (R5 funcMatches): Entry point 2, FHIRPathEngine.java:5951 (R5 funcMatchesFull): Entry point 3, FHIRPathEngine.java:5120 (R5 funcReplaceMatches): The same vulnerabilities exist in the dstu2, dstu2016may, dstu3, r4, and r4b modules, and the FHIRPathEngine is used in the validation module functionality. Why this is exploitable: No timeout mechanism covers FHIRPath evaluation, the ValidationTimeout class only protects InstanceValidator operations, not evaluateFhirPath() Java's Pattern.compile() with a pattern like (a+)+$ against input "aaaaaaaaaaaaaaaaaaaaaa!" causes exponential backtracking (O(2^n) time complexity) Impact CPU Exhaustion: The exponential backtracking in Java's regex engine consumes 100% of a CPU core for the duration of the hang (effectively infinite for sufficiently long input strings) for callers of FHIRPathEngine.
A regular expression with worst-case exponential or polynomial matching time is applied to untrusted input, causing excessive CPU use. Typical impact: denial of service when input is crafted to trigger backtracking.
CVE-2026-45367 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (6.9.7). Upgrading removes the vulnerable code path.
maven
ca.uhn.hapi.fhir:org.hl7.fhir.dstu2 (<= 6.9.6)ca.uhn.hapi.fhir:org.hl7.fhir.dstu2016may (<= 6.9.6)ca.uhn.hapi.fhir:org.hl7.fhir.dstu3 (<= 6.9.6)ca.uhn.hapi.fhir:org.hl7.fhir.r4 (<= 6.9.6)ca.uhn.hapi.fhir:org.hl7.fhir.r4b (<= 6.9.6)ca.uhn.hapi.fhir:org.hl7.fhir.r5 (<= 6.9.6)ca.uhn.hapi.fhir:org.hl7.fhir.validation (<= 6.9.6)ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli (<= 6.9.6)ca.uhn.hapi.fhir:org.hl7.fhir.dstu2 → 6.9.7 (maven)ca.uhn.hapi.fhir:org.hl7.fhir.dstu2016may → 6.9.7 (maven)ca.uhn.hapi.fhir:org.hl7.fhir.dstu3 → 6.9.7 (maven)ca.uhn.hapi.fhir:org.hl7.fhir.r4 → 6.9.7 (maven)ca.uhn.hapi.fhir:org.hl7.fhir.r4b → 6.9.7 (maven)ca.uhn.hapi.fhir:org.hl7.fhir.r5 → 6.9.7 (maven)ca.uhn.hapi.fhir:org.hl7.fhir.validation → 6.9.7 (maven)ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli → 6.9.7 (maven)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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Upgrade the following packages to resolve this vulnerability:
ca.uhn.hapi.fhir:org.hl7.fhir.dstu2 to 6.9.7 or laterca.uhn.hapi.fhir:org.hl7.fhir.dstu2016may to 6.9.7 or laterca.uhn.hapi.fhir:org.hl7.fhir.dstu3 to 6.9.7 or laterca.uhn.hapi.fhir:org.hl7.fhir.r4 to 6.9.7 or laterca.uhn.hapi.fhir:org.hl7.fhir.r4b to 6.9.7 or laterca.uhn.hapi.fhir:org.hl7.fhir.r5 to 6.9.7 or laterca.uhn.hapi.fhir:org.hl7.fhir.validation to 6.9.7 or laterca.uhn.hapi.fhir:org.hl7.fhir.validation.cli to 6.9.7 or laterKodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2026-45367 is a high-severity inefficient regular expression (ReDoS) vulnerability in ca.uhn.hapi.fhir:org.hl7.fhir.dstu2 (maven), affecting versions <= 6.9.6. It is fixed in 6.9.7. A regular expression with worst-case exponential or polynomial matching time is applied to untrusted input, causing excessive CPU use.
CVE-2026-45367 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
ca.uhn.hapi.fhir:org.hl7.fhir.dstu2 (maven) (versions <= 6.9.6)ca.uhn.hapi.fhir:org.hl7.fhir.dstu2016may (maven) (versions <= 6.9.6)ca.uhn.hapi.fhir:org.hl7.fhir.dstu3 (maven) (versions <= 6.9.6)ca.uhn.hapi.fhir:org.hl7.fhir.r4 (maven) (versions <= 6.9.6)ca.uhn.hapi.fhir:org.hl7.fhir.r4b (maven) (versions <= 6.9.6)ca.uhn.hapi.fhir:org.hl7.fhir.r5 (maven) (versions <= 6.9.6)ca.uhn.hapi.fhir:org.hl7.fhir.validation (maven) (versions <= 6.9.6)ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli (maven) (versions <= 6.9.6)Yes. CVE-2026-45367 is fixed in 6.9.7. Upgrade to this version or later.
Whether CVE-2026-45367 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
ca.uhn.hapi.fhir:org.hl7.fhir.dstu2 to 6.9.7 or laterca.uhn.hapi.fhir:org.hl7.fhir.dstu2016may to 6.9.7 or laterca.uhn.hapi.fhir:org.hl7.fhir.dstu3 to 6.9.7 or laterca.uhn.hapi.fhir:org.hl7.fhir.r4 to 6.9.7 or laterca.uhn.hapi.fhir:org.hl7.fhir.r4b to 6.9.7 or laterca.uhn.hapi.fhir:org.hl7.fhir.r5 to 6.9.7 or laterca.uhn.hapi.fhir:org.hl7.fhir.validation to 6.9.7 or laterca.uhn.hapi.fhir:org.hl7.fhir.validation.cli to 6.9.7 or later