# CVE-2015-6837: Null dereference in n/a

> Remote attackers can cause a denial of service via a crafted XML document due to a NULL pointer dereference in the PHP XSL extension.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 May 2016
- **Updated:** 6 Aug 2024
- **Also known as:** GHSA-6mjv-wh4q-f383, UBUNTU-CVE-2015-6837

## What is CVE-2015-6837?

CVE-2015-6837 is a high-severity vulnerability in Php Php, published on 16 May 2016. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The xsl_ext_function_php function in ext/xsl/xsltprocessor.c in PHP before 5.4.45, 5.5.x before 5.5.29, and 5.6.x before 5.6.13, when libxml2 before 2.9.2 is used, does not consider the possibility of a NULL valuePop return value before proceeding with a free operation during initial error checking, which allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via a crafted XML document, a different vulnerability than CVE-2015-6838.

## Which versions are affected by CVE-2015-6837?

It affects 2 products.


Products: Php Php, Xmlsoft Libxml2.

## How do I fix CVE-2015-6837?

Upgrade to a fixed version.

## Is CVE-2015-6837 being exploited?

There is no known exploitation of CVE-2015-6837 in the wild and no public exploit code.

## Other vulnerabilities in Php Php

- [CVE-2012-2688](https://insights.sbomify.com/CVE-2012-2688/): Integer overflow in n/a (critical 10.0)
- [CVE-2012-2376](https://insights.sbomify.com/CVE-2012-2376/): Memory corruption in n/a (critical 10.0)
- [CVE-2011-3268](https://insights.sbomify.com/CVE-2011-3268/): Memory corruption in n/a (critical 10.0)
- [CVE-2009-4143](https://insights.sbomify.com/CVE-2009-4143/): Other in n/a (critical 10.0)
- [CVE-2008-5557](https://insights.sbomify.com/CVE-2008-5557/): Memory corruption in n/a (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2015-6837 and fix it if it is affected.

What it is: CVE-2015-6837 is a high-severity vulnerability in Php Php, published on 16 May 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-2015-6837 in the wild and no public exploit code.

Affected product: Php Php. 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-2015-6837/ (Markdown: https://insights.sbomify.com/CVE-2015-6837/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2015-6837
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2015-6837
- OSV: https://osv.dev/vulnerability/CVE-2015-6837

---
From sbomify Insights: https://insights.sbomify.com/CVE-2015-6837/
Summaries are generated and may contain mistakes; the official description above is the record.