How severe is CVE-2015-6837?

CVE-2015-6837 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2015-6837 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 7% (93rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2015-6837?

CVE-2015-6837 primarily affects Php. In total, 64 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2015-6837?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2015-6837 published?

CVE-2015-6837 was published on 2016-05-16 and last updated on 2026-06-17.

CVE-2015-6837

CVE-2015-6837 is a high-severity vulnerability in Php with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 7% (93rd percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Php
Published: 2016-05-16
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2015-6837?: 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.
How severe is CVE-2015-6837?: CVE-2015-6837 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2015-6837 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 7% (93rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2015-6837?: CVE-2015-6837 primarily affects Php. In total, 64 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2015-6837?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2015-6837 published?: CVE-2015-6837 was published on 2016-05-16 and last updated on 2026-06-17.

References

Affected products (64)

cpe:2.3:a:php:php:5.6.0:alpha1:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.0:alpha2:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.0:alpha3:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.0:alpha4:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.0:alpha5:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.0:beta1:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.0:beta2:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.0:beta3:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.0:beta4:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.1:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.2:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.3:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.4:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.5:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.6:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.7:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.8:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.9:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.10:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.11:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.6.12:*:*:*:*:*:*:*
cpe:2.3:a:xmlsoft:libxml2:*:*:*:*:*:*:*:*
cpe:2.3:a:php:php:*:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.0:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.0:alpha1:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.0:alpha2:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.0:alpha3:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.0:alpha4:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.0:alpha5:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.0:alpha6:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.0:beta1:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.0:beta2:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.0:beta3:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.0:beta4:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.0:rc1:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.0:rc2:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.1:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.2:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.3:*:*:*:*:*:*:*
cpe:2.3:a:php:php:5.5.4:*:*:*:*:*:*:*

More vulnerabilities in Php

CVE-2015-0235 — Critical (CVSS 10.0): Heap-based buffer overflow in the __nss_hostname_digits_dots function in glibc 2.2, and other 2.x versions before 2.18,…
CVE-2012-2688 — Critical (CVSS 10.0): Unspecified vulnerability in the _php_stream_scandir function in the stream implementation in PHP before 5.3.15 and…
CVE-2012-2376 — Critical (CVSS 10.0): Buffer overflow in the com_print_typeinfo function in PHP 5.4.3 and earlier on Windows allows remote attackers to…
CVE-2011-3268 — Critical (CVSS 10.0): Buffer overflow in the crypt function in PHP before 5.3.7 allows context-dependent attackers to have an unspecified…
CVE-2009-4143 — Critical (CVSS 10.0): PHP before 5.2.12 does not properly handle session data, which has unspecified impact and attack vectors related to (1)…
CVE-2008-5557 — Critical (CVSS 10.0): Heap-based buffer overflow in ext/mbstring/libmbfl/filters/mbfilter_htmlent.c in the mbstring extension in PHP 4.3.0…

All CVEs affecting Php →

Threat intelligence

Threat-intel indicators referencing this CVE:

45.84.120.3 (ipv4-addr)
221.161.235.168 (ipv4-addr)
200.196.50.91 (ipv4-addr)
187.141.71.166 (ipv4-addr)
187.110.238.50 (ipv4-addr)
113.164.66.10 (ipv4-addr)
103.38.219.22 (ipv4-addr)
103.20.122.54 (ipv4-addr)