# CVE-2026-91819: MISP: HTTP Method Override Bypasses CSRF and Form Validation in BetterSecurityComponent

> Attackers can bypass CSRF and form validation in MISP by using HTTP method overrides, allowing unauthorized actions via crafted cross-site requests.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 15 Sep 2026
- **Updated:** 15 Sep 2026
- **Also known as:** GHSA-fx6r-c922-6mvg

## What is CVE-2026-91819?

CVE-2026-91819 is a medium-severity vulnerability in MISP, published on 15 Sep 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

Affected versions of MISP rely on CakePHP request-method override processing in a way that can disable CSRF and form-security validation.

CakePHP honors a _method field or X-HTTP-Method-Override header by rewriting the effective request method. For override values outside the normal write verbs POST, PUT, PATCH, and DELETE, CakePHP also clears the parsed request body. MISP’s security component then determines whether to perform _validatePost() and _validateCsrf() based on whether request data remains. With a value such as:

_method=GET

the body becomes empty before those checks run, so both protections are skipped. A cross-site form containing only that override can therefore reach actions whose parameters are taken from the URL rather than the request body

Version affected: ≤2.5.45

Weakness: CWE-352 (Cross-Site Request Forgery), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-91819?


## How do I fix CVE-2026-91819?

No fix has been published for CVE-2026-91819 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-91819 being exploited?

There is no known exploitation of CVE-2026-91819 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-91819 and fix it if it is affected.

What it is: CVE-2026-91819 is a medium-severity vulnerability in MISP, published on 15 Sep 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-91819 in the wild and no public exploit code.

Affected product: MISP. 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-2026-91819/ (Markdown: https://insights.sbomify.com/CVE-2026-91819/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-91819
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-91819
- OSV: https://osv.dev/vulnerability/CVE-2026-91819

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-91819/
Summaries are generated and may contain mistakes; the official description above is the record.