# CVE-2016-4028: Weak cryptography in n/a

> Attackers can exploit a padding oracle vulnerability in OX Guard to decrypt guest authentication tokens and steal user credentials.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 Dec 2016
- **Updated:** 6 Aug 2024
- **Also known as:** GHSA-qxh8-75pv-8vmg

## What is CVE-2016-4028?

CVE-2016-4028 is a high-severity vulnerability in n/a, published on 15 Dec 2016. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

An issue was discovered in Open-Xchange OX Guard before 2.4.0-rev8. OX Guard uses an authentication token to identify and transfer guest users' credentials.  The OX Guard API acts as a padding oracle by responding with different error codes depending on whether the provided token matches the encryption padding.  In combination with AES-CBC, this allows attackers to guess the correct padding.  Attackers may run brute-forcing attacks on the content of the guest authentication token and discover user credentials.  For a practical attack vector, the guest users needs to have logged in, the content of the guest user's "OxReaderID" cookie and the value of the "auth" parameter needs to be known to the attacker.

Weakness: CWE-255

## Which versions are affected by CVE-2016-4028?

It affects 1 product.


Products: Open-Xchange Ox Guard.

## How do I fix CVE-2016-4028?

No fix has been published for CVE-2016-4028 yet. Limit exposure of the affected software until one is available.

## Is CVE-2016-4028 being exploited?

There is no known exploitation of CVE-2016-4028 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2018-10986](https://insights.sbomify.com/CVE-2018-10986/): OX Guard 2.8.0 has CSRF. (high 8.8)
- [CVE-2015-8542](https://insights.sbomify.com/CVE-2015-8542/): Auth bypass in n/a (high 8.8)
- [CVE-2020-28944](https://insights.sbomify.com/CVE-2020-28944/): Denial of service in n/a (high 7.5)
- [CVE-2020-9426](https://insights.sbomify.com/CVE-2020-9426/): OX Guard 2.10.3 and earlier allows XSS. (medium 6.1)
- [CVE-2016-6851](https://insights.sbomify.com/CVE-2016-6851/): Cross-site scripting in n/a (medium 6.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-4028 and fix it if it is affected.

What it is: CVE-2016-4028 is a high-severity vulnerability in n/a, published on 15 Dec 2016. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2016-4028 in the wild and no public exploit code.

Affected product: n/a. 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-2016-4028/ (Markdown: https://insights.sbomify.com/CVE-2016-4028/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-4028
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-4028
- OSV: https://osv.dev/vulnerability/CVE-2016-4028

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-4028/
Summaries are generated and may contain mistakes; the official description above is the record.