CVE-2015-6838 [High] | Denial of Service in Php

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.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	3.80%	7.28%	+3.47%
2	2025-12-28	1.92%	3.80%	+1.88%
3	2025-12-27	—	1.92%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

3.80%

7.28%

+3.47%

2025-12-28

1.92%

3.80%

+1.88%

2025-12-27

—

1.92%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.5	3.0	HIGH	`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	3.9	3.6	[email protected]
5.0	2.0	MEDIUM	`AV:N/AC:L/Au:N/C:N/I:N/A:P` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:N) No authentication is required. Confidentiality impact (C:N) No confidentiality impact. Integrity impact (I:N) No integrity impact. Availability impact (A:P) Partial availability impact.	10.0	2.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.5

3.0

HIGH

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

3.9

3.6

[email protected]

5.0

2.0

MEDIUM

AV:N/AC:L/Au:N/C:N/I:N/A:P Click to expand

Access vector (AV:N): Can be exploited remotely over network reachability.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:N): No confidentiality impact.
Integrity impact (I:N): No integrity impact.
Availability impact (A:P): Partial availability impact.

10.0

2.9

[email protected]

OS Trackers for CVE-2015-6838

vendor	priority	summary	link
`gentoo`	normal	CVE-2015-6838: 1 GLSA(s) (201606-10), 1 atom(s) (dev-lang/php); latest impact normal.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2015-6838
`redhat`	low	—	https://access.redhat.com/security/cve/CVE-2015-6838
`ubuntu`	low	CVE-2015-6838 low priority: Ubuntu including 1 source packages (php5), 4 status rows across 4 suites (precise, trusty, upstream, vivid): released 3, needs-triage 1.	https://ubuntu.com/security/CVE-2015-6838

Affected software / configurations for CVE-2015-6838

Vendor	Product	Version	Raw CPE
php	php	5.6.0	cpe:2.3:a:php:php:5.6.0:alpha1::::::
php	php	5.6.0	cpe:2.3:a:php:php:5.6.0:alpha2::::::
php	php	5.6.0	cpe:2.3:a:php:php:5.6.0:alpha3::::::
php	php	5.6.0	cpe:2.3:a:php:php:5.6.0:alpha4::::::
php	php	5.6.0	cpe:2.3:a:php:php:5.6.0:alpha5::::::
php	php	5.6.0	cpe:2.3:a:php:php:5.6.0:beta1::::::
php	php	5.6.0	cpe:2.3:a:php:php:5.6.0:beta2::::::
php	php	5.6.0	cpe:2.3:a:php:php:5.6.0:beta3::::::
php	php	5.6.0	cpe:2.3:a:php:php:5.6.0:beta4::::::
php	php	5.6.1	cpe:2.3:a:php:php:5.6.1:::::::*
php	php	5.6.2	cpe:2.3:a:php:php:5.6.2:::::::*
php	php	5.6.3	cpe:2.3:a:php:php:5.6.3:::::::*
php	php	5.6.4	cpe:2.3:a:php:php:5.6.4:::::::*
php	php	5.6.5	cpe:2.3:a:php:php:5.6.5:::::::*
php	php	5.6.6	cpe:2.3:a:php:php:5.6.6:::::::*
php	php	5.6.7	cpe:2.3:a:php:php:5.6.7:::::::*
php	php	5.6.8	cpe:2.3:a:php:php:5.6.8:::::::*
php	php	5.6.9	cpe:2.3:a:php:php:5.6.9:::::::*
php	php	5.6.10	cpe:2.3:a:php:php:5.6.10:::::::*
php	php	5.6.11	cpe:2.3:a:php:php:5.6.11:::::::*
php	php	5.6.12	cpe:2.3:a:php:php:5.6.12:::::::*
xmlsoft	libxml2	<= 2.9.1	cpe:2.3:a:xmlsoft:libxml2::::::::
php	php	5.5.0	cpe:2.3:a:php:php:5.5.0:::::::*
php	php	5.5.0	cpe:2.3:a:php:php:5.5.0:alpha1::::::
php	php	5.5.0	cpe:2.3:a:php:php:5.5.0:alpha2::::::
php	php	5.5.0	cpe:2.3:a:php:php:5.5.0:alpha3::::::
php	php	5.5.0	cpe:2.3:a:php:php:5.5.0:alpha4::::::
php	php	5.5.0	cpe:2.3:a:php:php:5.5.0:alpha5::::::
php	php	5.5.0	cpe:2.3:a:php:php:5.5.0:alpha6::::::
php	php	5.5.0	cpe:2.3:a:php:php:5.5.0:beta1::::::
php	php	5.5.0	cpe:2.3:a:php:php:5.5.0:beta2::::::
php	php	5.5.0	cpe:2.3:a:php:php:5.5.0:beta3::::::
php	php	5.5.0	cpe:2.3:a:php:php:5.5.0:beta4::::::
php	php	5.5.0	cpe:2.3:a:php:php:5.5.0:rc1::::::
php	php	5.5.0	cpe:2.3:a:php:php:5.5.0:rc2::::::
php	php	5.5.1	cpe:2.3:a:php:php:5.5.1:::::::*
php	php	5.5.2	cpe:2.3:a:php:php:5.5.2:::::::*
php	php	5.5.3	cpe:2.3:a:php:php:5.5.3:::::::*
php	php	5.5.4	cpe:2.3:a:php:php:5.5.4:::::::*
php	php	5.5.5	cpe:2.3:a:php:php:5.5.5:::::::*
php	php	5.5.6	cpe:2.3:a:php:php:5.5.6:::::::*
php	php	5.5.7	cpe:2.3:a:php:php:5.5.7:::::::*
php	php	5.5.8	cpe:2.3:a:php:php:5.5.8:::::::*
php	php	5.5.9	cpe:2.3:a:php:php:5.5.9:::::::*
php	php	5.5.10	cpe:2.3:a:php:php:5.5.10:::::::*
php	php	5.5.11	cpe:2.3:a:php:php:5.5.11:::::::*
php	php	5.5.12	cpe:2.3:a:php:php:5.5.12:::::::*
php	php	5.5.13	cpe:2.3:a:php:php:5.5.13:::::::*
php	php	5.5.14	cpe:2.3:a:php:php:5.5.14:::::::*
php	php	5.5.15	cpe:2.3:a:php:php:5.5.15:::::::*
php	php	5.5.16	cpe:2.3:a:php:php:5.5.16:::::::*
php	php	5.5.17	cpe:2.3:a:php:php:5.5.17:::::::*
php	php	5.5.18	cpe:2.3:a:php:php:5.5.18:::::::*
php	php	5.5.19	cpe:2.3:a:php:php:5.5.19:::::::*
php	php	5.5.20	cpe:2.3:a:php:php:5.5.20:::::::*
php	php	5.5.21	cpe:2.3:a:php:php:5.5.21:::::::*
php	php	5.5.22	cpe:2.3:a:php:php:5.5.22:::::::*
php	php	5.5.23	cpe:2.3:a:php:php:5.5.23:::::::*
php	php	5.5.24	cpe:2.3:a:php:php:5.5.24:::::::*
php	php	5.5.25	cpe:2.3:a:php:php:5.5.25:::::::*
php	php	5.5.26	cpe:2.3:a:php:php:5.5.26:::::::*
php	php	5.5.27	cpe:2.3:a:php:php:5.5.27:::::::*
php	php	5.5.28	cpe:2.3:a:php:php:5.5.28:::::::*
php	php	<= 5.4.44	cpe:2.3:a:php:php::::::::

References for CVE-2015-6838

URL	Tags
http://php.net/ChangeLog-5.php
http://www.debian.org/security/2015/dsa-3358
http://www.securityfocus.com/bid/76733
http://www.securitytracker.com/id/1033548
https://bugs.php.net/bug.php?id=69782
https://security.gentoo.org/glsa/201606-10

URL

CVE-2015-6838

Exploit prediction scoring system (EPSS) score for CVE-2015-6838

Common vulnerability scoring system (CVSS) metrics for CVE-2015-6838

Weakness enumeration for CVE-2015-6838

OS Trackers for CVE-2015-6838

NVD evaluator notes for CVE-2015-6838

Affected software / configurations for CVE-2015-6838

References for CVE-2015-6838