# CVE-2026-89209: A vulnerability has been identified in Mendix SAML (Mendix 10 compatible) (All versions < V4.2.4), Mendix SAML (Mendix 11 compatible) (All v


- **Severity:** High 7.6 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 26 Oct 2026
- **Updated:** 26 Oct 2026
- **Also known as:** GHSA-c6gm-hvjc-mr8p

## What is CVE-2026-89209?

CVE-2026-89209 is a high-severity vulnerability in Siemens Mendix SAML (Mendix 10 compatible), published on 26 Oct 2026. 

### Official description

A vulnerability has been identified in Mendix SAML (Mendix 10 compatible) (All versions < V4.2.4), Mendix SAML (Mendix 11 compatible) (All versions < V4.2.4), Mendix SAML (Mendix 9 compatible) (All versions < V3.6.29). Affected versions of the module do not properly protect against SAML assertion replay in IdP-initiated authentication flows. This could allow unauthenticated remote attackers to gain unauthorized access to the application by replaying a valid SAML response.

Weakness: CWE-294 (Authentication Bypass by Capture-replay)

## Which versions are affected by CVE-2026-89209?


## How do I fix CVE-2026-89209?

No fix has been published for CVE-2026-89209 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-89209 being exploited?

There is no known exploitation of CVE-2026-89209 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89209 and fix it if it is affected.

What it is: CVE-2026-89209 is a high-severity vulnerability in Siemens Mendix SAML (Mendix 10 compatible), published on 26 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-89209 in the wild and no public exploit code.

Affected product: Siemens Mendix SAML (Mendix 10 compatible). No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-89209/ (Markdown: https://insights.sbomify.com/CVE-2026-89209/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89209
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89209
- OSV: https://osv.dev/vulnerability/CVE-2026-89209

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-89209/
Summaries are generated and may contain mistakes; the official description above is the record.