# CVE-2016-4449: XML external entity in n/a

> Attackers can exploit an XML external entity vulnerability in libxml2 to read arbitrary files or cause denial of service when validating mode is disabled.

- **Severity:** High 7.1 (`CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 9 Jun 2016
- **Updated:** 6 Aug 2024
- **Also known as:** DEBIAN-CVE-2016-4449, ECHO-9e53-9686-8b76, GHSA-r3pg-4m7c-9pvw, UBUNTU-CVE-2016-4449

## What is CVE-2016-4449?

CVE-2016-4449 is a high-severity vulnerability in Canonical Ubuntu Linux, published on 9 Jun 2016. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

XML external entity (XXE) vulnerability in the xmlStringLenDecodeEntities function in parser.c in libxml2 before 2.9.4, when not in validating mode, allows context-dependent attackers to read arbitrary files or cause a denial of service (resource consumption) via unspecified vectors.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2016-4449?

It affects 3 products.


Products: Canonical Ubuntu Linux, Debian Debian Linux, Xmlsoft Libxml2.

## How do I fix CVE-2016-4449?

Upgrade to a fixed version.

## Is CVE-2016-4449 being exploited?

There is no known exploitation of CVE-2016-4449 in the wild and no public exploit code.

## Other vulnerabilities in Canonical Ubuntu Linux

- [CVE-2020-11651](https://insights.sbomify.com/CVE-2020-11651/): SaltStack Salt Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2020-7247](https://insights.sbomify.com/CVE-2020-7247/): OpenSMTPD Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2019-16928](https://insights.sbomify.com/CVE-2019-16928/): Exim Out-of-bounds Write (critical 9.8, exploited in the wild)
- [CVE-2018-6789](https://insights.sbomify.com/CVE-2018-6789/): Exim Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2015-2590](https://insights.sbomify.com/CVE-2015-2590/): Oracle Java SE and Java SE Embedded Remote Code Execution (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-4449 and fix it if it is affected.

What it is: CVE-2016-4449 is a high-severity vulnerability in Canonical Ubuntu Linux, published on 9 Jun 2016. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2016-4449 in the wild and no public exploit code.

Affected product: Canonical Ubuntu Linux. 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-2016-4449/ (Markdown: https://insights.sbomify.com/CVE-2016-4449/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-4449
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-4449
- OSV: https://osv.dev/vulnerability/CVE-2016-4449

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From sbomify Insights: https://insights.sbomify.com/CVE-2016-4449/
Summaries are generated and may contain mistakes; the official description above is the record.