CVE-2015-6834

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2022-05-17. NVD baseline CVSS 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Weaponized
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 47%CVSS: 9.8Exploit: NoneExposed: 0

A fix is available — apply it.

Multiple use-after-free vulnerabilities in PHP before 5.4.45, 5.5.x before 5.5.29, and 5.6.x before 5.6.13 allow remote attackers to execute arbitrary code via vectors related to (1) the Serializable interface, (2) the SplObjectStorage class, and (3) the SplDoublyLinkedList class, which are mishandled during unserialization.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
75(Track*)
EG Risk 75/100SSVC: 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
Severity98% × 45%
Exploitation65% × 40%
Automatability30% × 15%
Action: Watch closely — could escalate to Attend.
EPSS
98.7%
KEV
Not listed

Published

May 16, 2016

Last Modified

May 6, 2026

Advisory Details (7)

Auto-updated May 8, 2026
No patch confirmed yet.
generic

[SECURITY] [DSA 3358-1] php5 security update

http://www.debian.org/security/2015/dsa-3358
generic

PHP: PHP 5 ChangeLog

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

PHP: Multiple vulnerabilities (GLSA 201606-10) — Gentoo security

https://security.gentoo.org/glsa/201606-10
generic

PHP :: Sec Bug #70366 :: yet another use-after-free vulnerability in unserialize() with SplDoublyLinkedL

https://bugs.php.net/bug.php?id=70366
generic

PHP :: Sec Bug #70365 :: yet another use-after-free vulnerability in unserialize() with SplObjectStorage

https://bugs.php.net/bug.php?id=70365
generic

PHP :: Sec Bug #70172 :: Use After Free Vulnerability in unserialize()

https://bugs.php.net/bug.php?id=70172
generic
http://www.securityfocus.com/bid/76649

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuphp5-fpm (5.6.4+dfsg-4ubuntu6.3) @ vivid2026-05-20ubuntu
redhatrh-php56-php-0:5.6.5-8.el72016-03-15redhat

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.

All Vendor Advisories

(2)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 8× in last 7d / 27× 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. 2026-07-24 14:13 UTCEPSS rescore
  2. 2026-07-23 01:19 UTCEG score recompute
  3. 2026-07-23 00:21 UTCEG score recompute
  4. 2026-07-22 21:59 UTCEG score recompute
  5. 2026-07-22 14:04 UTCEPSS rescore
  6. 2026-07-20 17:03 UTCEPSS rescore
  7. 2026-07-19 02:26 UTCEPSS rescore
  8. 2026-07-19 02:26 UTCEPSS rescore
  9. 2026-07-16 16:59 UTCEPSS rescore
  10. 2026-07-15 16:54 UTCEPSS rescore
  11. 2026-07-15 16:54 UTCEPSS rescore
  12. 2026-07-13 22:26 UTCEPSS rescore
  13. 2026-07-13 22:26 UTCEPSS rescore
  14. 2026-07-12 05:42 UTCEPSS rescore
  15. 2026-07-11 08:23 UTCEPSS rescore
  16. 2026-07-09 19:05 UTCEPSS rescore
  17. 2026-07-09 19:05 UTCEPSS rescore
  18. 2026-07-06 02:20 UTCEPSS rescore
  19. 2026-07-01 15:02 UTCEPSS rescore
  20. 2026-06-30 23:19 UTCEPSS rescore
  21. 2026-06-30 23:19 UTCEPSS rescore
  22. 2026-06-29 14:03 UTCEPSS rescore
  23. 2026-06-29 14:03 UTCEPSS rescore
  24. 2026-06-28 04:53 UTCEPSS rescore
  25. 2026-06-27 03:05 UTCEPSS rescore
Show 65 more
  1. 2026-06-25 13:47 UTCEPSS rescore
  2. 2026-06-25 13:47 UTCEPSS rescore
  3. 2026-06-24 14:02 UTCEPSS rescore
  4. 2026-06-24 14:02 UTCEPSS rescore
  5. 2026-06-23 21:30 UTCEPSS rescore
  6. 2026-06-21 14:54 UTCEPSS rescore
  7. 2026-06-21 14:54 UTCEPSS rescore
  8. 2026-06-21 01:57 UTCEPSS rescore
  9. 2026-06-21 01:57 UTCEPSS rescore
  10. 2026-06-18 17:50 UTCEPSS rescore
  11. 2026-06-17 17:50 UTCEPSS rescore
  12. 2026-06-17 17:49 UTCEPSS rescore
  13. 2026-06-16 17:50 UTCEPSS rescore
  14. 2026-06-16 17:50 UTCEPSS rescore
  15. 2026-06-15 17:45 UTCEPSS rescore
  16. 2026-06-13 22:57 UTCEPSS rescore
  17. 2026-06-12 23:09 UTCEPSS rescore
  18. 2026-06-12 23:09 UTCEPSS rescore
  19. 2026-06-11 13:57 UTCEPSS rescore
  20. 2026-06-11 13:57 UTCEPSS rescore
  21. 2026-06-10 22:15 UTCEPSS rescore
  22. 2026-06-10 13:18 UTCEPSS rescore
  23. 2026-06-07 15:22 UTCEPSS rescore
  24. 2026-06-06 13:45 UTCEPSS rescore
  25. 2026-06-05 22:44 UTCEPSS rescore
  26. 2026-06-05 06:08 UTCEPSS rescore
  27. 2026-06-05 06:08 UTCEPSS rescore
  28. 2026-06-02 20:10 UTCEPSS rescore
  29. 2026-05-31 22:28 UTCEPSS rescore
  30. 2026-05-31 22:28 UTCEPSS rescore
  31. 2026-05-31 00:14 UTCEPSS rescore
  32. 2026-05-29 13:41 UTCEPSS rescore
  33. 2026-05-28 13:42 UTCEPSS rescore
  34. 2026-05-28 13:42 UTCEPSS rescore
  35. 2026-05-27 13:38 UTCEPSS rescore
  36. 2026-05-27 13:38 UTCEPSS rescore
  37. 2026-05-24 16:43 UTCEPSS rescore
  38. 2026-05-22 21:15 UTCEPSS rescore
  39. 2026-05-21 22:40 UTCEPSS rescore
  40. 2026-05-20 22:37 UTCEPSS rescore
  41. 2026-05-20 22:37 UTCEPSS rescore
  42. 2026-05-20 11:21 UTCEPSS rescore
  43. 2026-05-20 11:21 UTCEPSS rescore
  44. 2026-05-20 11:21 UTCEPSS rescore
  45. 2026-05-20 09:14 UTCVendor advisory
  46. 2026-05-20 09:14 UTCGHSA enrichment
  47. 2026-05-20 05:12 UTCVendor advisory
  48. 2026-05-20 05:12 UTCGHSA enrichment
  49. 2026-05-20 01:14 UTCVendor advisory
  50. 2026-05-20 01:14 UTCGHSA enrichment
  51. 2026-05-19 20:58 UTCVendor advisory
  52. 2026-05-19 20:58 UTCGHSA enrichment
  53. 2026-05-19 16:56 UTCVendor advisory
  54. 2026-05-19 16:56 UTCGHSA enrichment
  55. 2026-05-19 12:49 UTCVendor advisory
  56. 2026-05-19 12:49 UTCGHSA enrichment
  57. 2026-05-19 08:48 UTCVendor advisory
  58. 2026-05-19 08:47 UTCGHSA enrichment
  59. 2026-05-19 04:50 UTCVendor advisory
  60. 2026-05-19 04:50 UTCGHSA enrichment
  61. 2026-05-19 00:51 UTCEG score recompute
  62. 2026-05-19 00:51 UTCVendor advisory
  63. 2026-05-19 00:51 UTCGHSA enrichment
  64. 2026-05-18 21:30 UTCEPSS rescore
  65. 2026-05-18 21:30 UTCEPSS rescore

Publicly available exploits

(2 references)

Working exploit code is in the public domain (2 Exploit-DB entries). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Exploit-DBEDB-38120✓ verified
    First seen Sep 9, 2015

    PHP 5.4/5.5/5.6 - SplDoublyLinkedList 'Unserialize()' Use-After-Free

    Open source ↗
  • Exploit-DBEDB-38122✓ verified
    First seen Sep 9, 2015

    PHP 5.4/5.5/5.6 - SplObjectStorage 'Unserialize()' Use-After-Free

    Open source ↗

Frequently asked(5)

What is CVE-2015-6834?
CVE-2015-6834 is a critical vulnerability published on May 16, 2016. Multiple use-after-free vulnerabilities in PHP before 5.4.45, 5.5.x before 5.5.29, and 5.6.x before 5.6.13 allow remote attackers to execute arbitrary code via vectors related to (1) the Serializable interface, (2) the SplObjectStorage class, and (3) the SplDoublyLinkedList class, which are…
When was CVE-2015-6834 disclosed?
CVE-2015-6834 was first published in the National Vulnerability Database on May 16, 2016, with the most recent update on May 6, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2015-6834 actively exploited?
CVE-2015-6834 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 98.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2015-6834?
CVE-2015-6834 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2015-6834?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2015-6834, 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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