# CVE-2026-45119: MyBB: ACP UTF-8 Conversion CSRF

> Attackers can trigger database table encoding changes and service disruption via CSRF in the Admin CP UTF-8 Conversion module.

- **Severity:** Medium 4.6 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:L`)
- **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:** 18 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** GHSA-p48q-4vgf-q7x8

## What is CVE-2026-45119?

CVE-2026-45119 is a medium-severity vulnerability in mybb, published on 18 Aug 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

MyBB is free and open source forum software. Prior to 1.8.40, the Admin CP UTF-8 Conversion module does not validate certain requests correctly, allowing same-site attackers to alter table encoding and deny service with a specially crafted URL. The do=all control flow in admin/modules/tools/system_health.php performs ALTER TABLE operations, column rewrite phases, and fulltext index rebuilds on GET requests for the database table named by the table parameter without request verification. The uniquely identifying implementation details include GET requests without request verification. This issue is fixed in version 1.8.40.

Weakness: CWE-352 (Cross-Site Request Forgery)

## Which versions are affected by CVE-2026-45119?


## How do I fix CVE-2026-45119?

No fix has been published for CVE-2026-45119 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-45119 being exploited?

There is no known exploitation of CVE-2026-45119 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45119 and fix it if it is affected.

What it is: CVE-2026-45119 is a medium-severity vulnerability in mybb, published on 18 Aug 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-2026-45119 in the wild and no public exploit code.

Affected product: mybb. 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-2026-45119/ (Markdown: https://insights.sbomify.com/CVE-2026-45119/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45119
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45119
- OSV: https://osv.dev/vulnerability/CVE-2026-45119

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45119/
Summaries are generated and may contain mistakes; the official description above is the record.