Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
HAPI FHIR's FHIRPath engine, in the org.hl7.fhir packages for dstu2, dstu2016may, dstu3, r4, r4b, r5, validation, and validation.cli before 6.9.7, passes user-supplied regular expressions from matches(), matchesFull() and replaceMatches() directly to Java regex functions with no complexity limit or timeout. An attacker who can submit a resource to a validator that evaluates such expressions can supply a pattern that causes catastrophic backtracking, exhausting CPU and causing denial of service. Upgrade to version 6.9.7 or later. The source gives no workaround.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 7.5 | High | 3.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0068, the 52nd percentile, on 9 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:16 UTC First seen by agentprime
- 31 Oct 2026, 14:16 UTC Confirmed by OSV