CVE-2015-6838

What it is

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 after the principal argument loop, 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-2015-6837.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of service disruption.

Exploit odds

8.1% chance of exploitation in the next 30 days (EPSS).

Fix

No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

1. 2016-05-16 10:59 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 00:31 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 8.1% in the next 30 days (EPSS).
• Severity: 7.5 HIGH (CVSS).
• Fix: none linked yet, which raises it.

Details

Published

2016-05-16 10:59 UTC

Last modified

2026-06-17 00:31 UTC

Exploit probability

8.1% · EPSS, next 30 days

Record status

Modified

Affected

• PHP 5.6.0
• PHP 5.6.1
• PHP 5.6.2
• PHP 5.6.3
• PHP 5.6.4
• PHP 5.6.5
• PHP 5.6.6
• PHP 5.6.7

Attack profile CVSS 3.0 · 7.5

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2015-6838.md and follow it. Check whether this project is affected by CVE-2015-6838. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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