# CVE-2026-124481: OpenEMR before 8.4.0 Cross-Patient Payment Tampering via Rainforest Portal Payments

Status: published. Published: 2026-11-08. Updated: 2026-11-12.

OpenEMR before 8.4.0 contains an improper authorization vulnerability in Rainforest patient portal payments that trusts browser-supplied patientId, encounter, and amount values instead of deriving them from the portal session. Authenticated portal patients can tamper with JSON sent to portal_payment.rainforest.php so the payin.authorized webhook writes forged ar_activity credits to other patients' encounters exceeding the amount actually paid.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- openemr / openemr: ≥ 0; < 8.4.0 (affected, semver); 8.4.0 (unaffected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 7.1 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 6.5 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N; source: CNA: VulnCheck

- CVSS 4.0: 7.1 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 6.5 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.24% as of 2026-11-10; percentile 15.72%

- SSVC: exploitation poc; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-639

## Exploit evidence

- exploit: https://github.com/openemr/openemr/security/advisories/GHSA-525m-fch5-vqqm (ADP: CISA-ADP)

## References

- https://github.com/openemr/openemr/security/advisories/GHSA-525m-fch5-vqqm (CNA: VulnCheck; vendor-advisory)

- https://www.vulncheck.com/advisories/openemr-before-8.4.0-cross-patient-payment-tampering-via-rainforest-portal-payments (CNA: VulnCheck; third-party-advisory)

- https://github.com/openemr/openemr/security/advisories/GHSA-525m-fch5-vqqm (ADP: CISA-ADP; exploit)

- https://github.com/openemr/openemr/security/advisories/GHSA-525m-fch5-vqqm (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/openemr-before-8.4.0-cross-patient-payment-tampering-via-rainforest-portal-payments (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-124481; retrieved 2026-11-12; source updated 2026-11-12

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-124481; retrieved 2026-11-11; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-124481; retrieved 2026-11-11; source updated Not reported

Revision: e964515947bd7e2fd670a809a7b350ee2bfa7dc482fe4a6e5825a46abde3cd3d

Canonical: https://y2.dev/cve/CVE-2026-124481

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.