What is the CVSS score of CVE-2015-8866?

CVE-2015-8866 has a CVSS 3.1 base score of 9.6 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H. EPSS exploitation probability: 3.5%.

Is there a public PoC exploit available for CVE-2015-8866?

Yes, a public proof-of-concept exploit is available for CVE-2015-8866. Prioritise patching immediately. EPSS: 3.5%.

Is there a patch available for CVE-2015-8866?

Yes, a patch is available for CVE-2015-8866. Update the affected software to the latest version immediately.

PHP CVE-2015-8866

CRITICAL

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

2016-05-22 cve@mitre.org

PHP XXE Canonical Leap Linux Enterprise Software Development Kit Ubuntu Linux Suse Opensuse Linux Enterprise Module For Web Scripting

9.6

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-611 OWASP Top 10:2025 A02:2025 - Security Misconfiguration ASVS 5.0 V13 - Configuration XML external entity prevention MITRE ATT&CK 2 techniques across 2 tactics: Initial Access, Collection The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 9.6 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, user interaction required. Public proof-of-concept exploit code is available. EPSS exploitation probability: 3.53%.
Exploit ScenarioDerived	A remote attacker could read arbitrary files or perform SSRF through XML processing by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

Act Now Prioritize within 24-48h. Why: CRITICAL severity + public POC available.

Patch available 3.5% exploitation probability (EPSS)

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AnalysisAI

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. Rated critical severity (CVSS 9.6), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Disable external entity processing in XML parsers, use JSON instead of XML where possible.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as XML External Entity (XXE) (CWE-611), which allows attackers to read arbitrary files or perform SSRF through XML processing. 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. Affected products include: Php, Canonical Ubuntu Linux, Opensuse Leap, Opensuse, Suse Linux Enterprise Module For Web Scripting. Version information: before 5.5.22.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 9.6 CRITICAL

AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

DescriptionCVE.org

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.

Threat Intelligence Overview

EPSS Score

3.5%

Top 12% exploitable

Exploit

POC

Public exploit code exists

Data Quality

3 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity CRITICAL

CISA KEV No

Public POC Yes

EPSS 3.5%

Patch available Yes

Active threat No

Deciding rule

CRITICAL severity + public POC available

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

Poc

System Exposure· derived

Open

Automatable· derived

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +4

CVSS: +48

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

XML External Entity Injection HIGH

XML External Entity (XXE) attacks exploit XML parsers that process Document Type Definitions (DTDs) without proper restrictions.

Affected Products (CPE)CVE.org

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:*:*:*:*:*:*

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References

Advisories & patches

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

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