# HAPI FHIR: Incomplete fix for CVE-2026-45367: DSTU2 FHIRPathEngine.matches() missing RegexTimeout protection allows ReDoS

Advisory record · `GHSA-fxj4-p9xp-37v5`

- **Identifiers:** `GHSA-fxj4-p9xp-37v5` · `CVE-2026-55470`
- **State:** Confirmed
- **Severity:** CVSS 7.5 High
- **Critical:** No
- **Weakness (CWE):** [CWE-1333](https://cwe.mitre.org/data/definitions/1333.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md)
- **Published:** 17 Jun 2026
- **Updated:** 17 Jun 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 17 Jun 2026, 18:47 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `ca.uhn.hapi.fhir:org.hl7.fhir.dstu2` (Maven): affected `<6.9.10`; fixed in `6.9.10`
- `ca.uhn.hapi.fhir:org.hl7.fhir.convertors` (Maven): affected `<6.9.10`; fixed in `6.9.10`
- `ca.uhn.hapi.fhir:org.hl7.fhir.validation` (Maven): affected `<6.9.10`; fixed in `6.9.10`
- `ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli` (Maven): affected `<6.9.10`; fixed in `6.9.10`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> The Maven package ca.uhn.hapi.fhir:org.hl7.fhir.dstu2 (and the related org.hl7.fhir.convertors, org.hl7.fhir.validation, and org.hl7.fhir.validation.cli modules) is vulnerable in versions before 6.9.10. The DSTU2 FHIRPathEngine matches() function lacks regex timeout protection, so a user-supplied FHIRPath expression with a catastrophically backtracking regular expression can exhaust CPU. No authentication is required. Upgrade to version 6.9.10, where the fix is listed.

Written 3 Nov 2026.

## 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

- 7.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`, from 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, 14:20 UTC: First seen by agentprime
- 31 Oct 2026, 14:20 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-fxj4-p9xp-37v5)

## Sources

- [GitHub Advisory Database: GHSA-fxj4-p9xp-37v5](https://github.com/advisories/GHSA-fxj4-p9xp-37v5)
- [OSV: GHSA-fxj4-p9xp-37v5](https://osv.dev/vulnerability/GHSA-fxj4-p9xp-37v5)
- <https://github.com/hapifhir/org.hl7.fhir.core/security/advisories/GHSA-fxj4-p9xp-37v5>
- <https://github.com/hapifhir/org.hl7.fhir.core>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-fxj4-p9xp-37v5>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-fxj4-p9xp-37v5/>. Everything for agents: <https://agentprime.io/llms.txt>.