# CVE-2016-9838: Privilege escalation in n/a

> Attackers can hijack registered user accounts and modify group mappings, usernames, and passwords via improper session data filtering in Joomla registration forms.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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:** 16 Dec 2016
- **Updated:** 6 Aug 2024
- **Also known as:** GHSA-r7gw-fgrc-gxxj

## What is CVE-2016-9838?

CVE-2016-9838 is a high-severity vulnerability in Joomla Joomla\!, published on 16 Dec 2016. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in components/com_users/models/registration.php in Joomla! before 3.6.5. Incorrect filtering of registration form data stored to the session on a validation error enables a user to gain access to a registered user's account and reset the user's group mappings, username, and password, as demonstrated by submitting a form that targets the `registration.register` task.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2016-9838?

It affects 1 product.


Products: Joomla Joomla\!.

## How do I fix CVE-2016-9838?

No fix has been published for CVE-2016-9838 yet. Limit exposure of the affected software until one is available.

## Is CVE-2016-9838 being exploited?

There is no known exploitation of CVE-2016-9838 in the wild and no public exploit code.

Public exploit code:

- Joomla! < 3.6.4 - Admin Takeover (exploitdb)
- cve-2016-9838 (github_poc): https://github.com/cved-sources/cve-2016-9838

## Other vulnerabilities in Joomla Joomla\!

- [CVE-2016-10033](https://insights.sbomify.com/CVE-2016-10033/): PHPMailer Command Injection (critical 9.8, exploited in the wild)
- [CVE-2023-23752](https://insights.sbomify.com/CVE-2023-23752/): Joomla! Improper Access Control (medium 5.3, exploited in the wild)
- [CVE-2026-48902](https://insights.sbomify.com/CVE-2026-48902/): Joomla! Core - [20260518] - Transport encryption downgrade for password and username reset links (critical 9.8)
- [CVE-2025-25226](https://insights.sbomify.com/CVE-2025-25226/): [20250401] - Joomla Framework - SQL injection vulnerability in quoteNameStr method of Database package (critical 9.8)
- [CVE-2022-23795](https://insights.sbomify.com/CVE-2022-23795/): [20220303] - Core - User row are not bound to a authentication mechanism (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-9838 and fix it if it is affected.

What it is: CVE-2016-9838 is a high-severity vulnerability in Joomla Joomla\!, published on 16 Dec 2016. 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-2016-9838 in the wild and no public exploit code.

Affected product: Joomla Joomla\!. 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-2016-9838/ (Markdown: https://insights.sbomify.com/CVE-2016-9838/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-9838
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-9838
- OSV: https://osv.dev/vulnerability/CVE-2016-9838

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-9838/
Summaries are generated and may contain mistakes; the official description above is the record.