# CVE-2026-46482: MyBB: Security Question insufficient validation

> Attackers can bypass the registration security question CAPTCHA by providing invalid identifiers, allowing automated account creation.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 18 Aug 2026
- **Updated:** 18 Aug 2026
- **Also known as:** GHSA-v2h7-4jp7-j6hh

## What is CVE-2026-46482?

CVE-2026-46482 is a medium-severity vulnerability in mybb, published on 18 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

### Impact
The registration component does not validate the text-based _Security Question_ CAPTCHA correctly, allowing attackers to bypass the challenge via a specially crafted value.

[CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N](https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N)

### Details
The public _Registration_ workflow ([`member.php?action=do_register`](https://github.com/mybb/mybb/blob/mybb_1839/member.php#L262-L307)) accepts a hidden field `question_id` — expected to match the question session identifier (`mybb_questionsessions.sid`) — and validates the challenge answer without a fail-closed fallback for invalid identifiers. If the value is blank, forged, or expired, the request continues without a question-related error.

### Patches
MyBB 1.8.(...) resolves this issue with the following changes:

- Commit: https://github.com/mybb/mybb/commit/
  - `.patch`: https://github.com/mybb/mybb/commit/.patch

### References
- Release Notes: https://mybb.com/versions/1.8.(...)/

### For more information
Go to [mybb.com/security](https://mybb.com/security/) to report possible security concerns or to learn more about security research at MyBB.

### Contact
The security team can be reached at [security@mybb.com](mailto:security@mybb.com).

Weakness: CWE-636 (Not Failing Securely)

## Which versions are affected by CVE-2026-46482?


## How do I fix CVE-2026-46482?

No fix has been published for CVE-2026-46482 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-46482 being exploited?

There is no known exploitation of CVE-2026-46482 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-46482 and fix it if it is affected.

What it is: CVE-2026-46482 is a medium-severity vulnerability in mybb, published on 18 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-46482 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-2026-46482/ (Markdown: https://insights.sbomify.com/CVE-2026-46482/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46482
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46482
- OSV: https://osv.dev/vulnerability/CVE-2026-46482

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46482/
Summaries are generated and may contain mistakes; the official description above is the record.