CVE-2015-8866

CVE-2015-8866 is a critical-severity vulnerability in Php with a CVSS 3.x base score of 9.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-611.

Key facts

• Severity: Critical (CVSS 3.x base score 9.6)
• CVSS v2: 6.8
• EPSS exploit prediction: 4% (89th percentile)
• Actively exploited: Not listed in CISA KEV
• Weakness: CWE-611
• Affected product: Php
• Published: 2016-05-22
• Last modified: 2026-06-17

Description

ext/libxml/libxml.c in PHP before 5.5.22 and 5.6.x before 5.6.6, when PHP-FPM is used, does not isolate each thread from libxml_disable_entity_loader changes in other threads, which allows remote attackers to conduct XML External Entity (XXE) and XML Entity Expansion (XEE) attacks via a crafted XML document, a related issue to CVE-2015-5161.

Frequently asked questions

What is CVE-2015-8866?

ext/libxml/libxml.c in PHP before 5.5.22 and 5.6.x before 5.6.6, when PHP-FPM is used, does not isolate each thread from libxml_disable_entity_loader changes in other threads, which allows remote attackers to conduct XML External Entity (XXE) and XML Entity Expansion (XEE) attacks via a crafted XML document, a related issue to CVE-2015-5161.

How severe is CVE-2015-8866?

CVE-2015-8866 has a CVSS 3.x base score of 9.6, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2015-8866 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (89th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2015-8866?

CVE-2015-8866 primarily affects Php. In total, 9 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2015-8866?

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

When was CVE-2015-8866 published?

CVE-2015-8866 was published on 2016-05-22 and last updated on 2026-06-17.

References

• http://git.php.net/?p=php-src.git%3Ba=commit%3Bh=de31324c221c1791b26350ba106cc26bad23ace9
• http://lists.opensuse.org/opensuse-security-announce/2016-05/msg00031.html
• http://lists.opensuse.org/opensuse-security-announce/2016-05/msg00033.html
• http://lists.opensuse.org/opensuse-security-announce/2016-05/msg00056.html
• http://rhn.redhat.com/errata/RHSA-2016-2750.html
• http://www.openwall.com/lists/oss-security/2016/04/24/1
• http://www.php.net/ChangeLog-5.php
• http://www.securityfocus.com/bid/87470
• http://www.ubuntu.com/usn/USN-2952-1
• http://www.ubuntu.com/usn/USN-2952-2
• https://bugs.launchpad.net/ubuntu/+source/php5/+bug/1509817
• https://bugs.php.net/bug.php?id=64938

Affected products (9)

• cpe:2.3:a:php:php:*:*:*:*:*:*:*:*
• cpe:2.3:o:canonical:ubuntu_linux:12.04:*:*:*:-:*:*:*
• cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:esm:*:*:*
• cpe:2.3:o:canonical:ubuntu_linux:15.10:*:*:*:*:*:*:*
• cpe:2.3:o:opensuse:leap:42.1:*:*:*:*:*:*:*
• cpe:2.3:o:opensuse:opensuse:13.2:*:*:*:*:*:*:*
• cpe:2.3:o:suse:linux_enterprise_module_for_web_scripting:12:*:*:*:*:*:*:*
• cpe:2.3:o:suse:linux_enterprise_software_development_kit:12:-:*:*:*:*:*:*
• cpe:2.3:o:suse:linux_enterprise_software_development_kit:12:sp1:*:*:*:*:*:*

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 →

Other CWE-611 (Improper Restriction of XML External Entity Reference (XXE)) vulnerabilities

• CVE-2022-22486 — Critical (CVSS 10.0): IBM Tivoli Workload Scheduler 9.4, 9.5, and 10.1 is vulnerable to an XML External Entity Injection (XXE) attack when…
• CVE-2019-14678 — Critical (CVSS 10.0): SAS XML Mapper 9.45 has an XML External Entity (XXE) vulnerability that can be leveraged by malicious attackers in…
• CVE-2015-9280 — Critical (CVSS 10.0): MailEnable before 8.60 allows XXE via an XML document in the request.aspx Options parameter.
• CVE-2018-1000838 — Critical (CVSS 10.0): autopsy version <= 4.9.0 contains a XML External Entity (XXE) vulnerability in CaseMetadata XML Parser that can result…
• CVE-2018-1000837 — Critical (CVSS 10.0): UML Designer version <= 8.0.0 contains a XML External Entity (XXE) vulnerability in XML parser for plugins that can…
• CVE-2018-1000835 — Critical (CVSS 10.0): KeePassDX version <= 2.5.0.0beta17 contains a XML External Entity (XXE) vulnerability in kdbx file parser that can…

Browse all CWE-611 (Improper Restriction of XML External Entity Reference (XXE)) vulnerabilities →

Threat intelligence

Threat-intel indicators referencing this CVE:

• 221.182.185.190 (ipv4-addr)
• 183.182.99.92 (ipv4-addr)
• 61.143.227.17 (ipv4-addr)
• 103.153.190.105 (ipv4-addr)
• 58.56.128.190 (ipv4-addr)
• 36.249.60.142 (ipv4-addr)
• 220.161.52.149 (ipv4-addr)
• 188.44.20.32 (ipv4-addr)