CVE-2015-8866

CRITICALNVD 9.69.6—
EchelonGraph scoreMEDIUM confidence

Score 9.6 from GitHub Security Advisory (severity: CRITICAL) published 2022-05-14. NVD baseline CVSS 9.6; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
9.6EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 4%CVSS: 9.6Exploit: None knownExposed: 0

A fix is available — apply it.

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.

CVSS v3
9.6
EG Score
9.6(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity96% × 45%
Exploitation4% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
4%
EPSS %ILE
90%
KEV
Not listed

Published

May 22, 2016

Last Modified

June 17, 2026

Advisory Details (4)

Auto-updated May 9, 2026
No patch confirmed yet.
generic
http://www.securityfocus.com/bid/87470
generic

PHP: PHP 5 ChangeLog

http://www.php.net/ChangeLog-5.php
generic

oss-security - Re: CVE request: PHP issues fixed in 7.0.5, 5.6.20 and 5.5.34 releases

http://www.openwall.com/lists/oss-security/2016/04/24/1
generic
http://rhn.redhat.com/errata/RHSA-2016-2750.html

Vendor Advisories for CVE-2015-8866(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatrh-php56-php-pear-1:1.9.5-4.el72016-11-15redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 9× in last 7d / 34× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-25 14:13 UTCEPSS rescore
  2. 2026-07-24 14:13 UTCEPSS rescore
  3. 2026-07-23 14:14 UTCEPSS rescore
  4. 2026-07-23 01:20 UTCEG score recompute
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  6. 2026-07-22 22:00 UTCEG score recompute
  7. 2026-07-22 14:04 UTCEPSS rescore
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  1. 2026-07-08 15:10 UTCEPSS rescore
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  44. 2026-05-31 22:28 UTCEPSS rescore
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  56. 2026-05-22 21:15 UTCEPSS rescore
  57. 2026-05-22 20:15 UTCEG score recompute
  58. 2026-05-22 20:15 UTCVendor advisory
  59. 2026-05-22 20:15 UTCGHSA enrichment
  60. 2026-05-21 22:40 UTCEPSS rescore
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  66. 2026-05-18 21:30 UTCEPSS rescore
  67. 2026-05-18 21:30 UTCEPSS rescore

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2015-8866?
CVE-2015-8866 is a critical vulnerability published on May 22, 2016. 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 libxmldisableentity_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…
When was CVE-2015-8866 disclosed?
CVE-2015-8866 was first published in the National Vulnerability Database on May 22, 2016, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2015-8866 actively exploited?
CVE-2015-8866 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 4% probability of exploitation in the next 30 days, which ranks it in the top 10.5% of all scored CVEs.
What is the CVSS score of CVE-2015-8866?
CVE-2015-8866 has a CVSS v3 base score of 9.6 (NVD).
How do I remediate CVE-2015-8866?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2015-8866, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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