CVE-2015-6835

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: 37%CVSS: 9.8Exploit: NoneExposed: 0

A fix is available — apply it.

The session deserializer in PHP before 5.4.45, 5.5.x before 5.5.29, and 5.6.x before 5.6.13 mishandles multiple php_var_unserialize calls, which allow remote attackers to execute arbitrary code or cause a denial of service (use-after-free) via crafted session content.

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
98.4%
KEV
Not listed

Published

May 16, 2016

Last Modified

May 6, 2026

Advisory Details (5)

Auto-updated May 8, 2026
No patch confirmed yet.
generic
http://www.securityfocus.com/bid/76734
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 #70219 :: Use after free vulnerability in session deserializer

https://bugs.php.net/bug.php?id=70219

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuphp5-fpm (5.3.10-1ubuntu3.20) @ precise2026-05-20ubuntu
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 12× 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.

Showing the most recent 100 of 102 total refreshes for this CVE.

  1. 2026-07-24 14:13 UTCEPSS rescore
  2. 2026-07-23 14:14 UTCEPSS rescore
  3. 2026-07-23 01:19 UTCEG score recompute
  4. 2026-07-23 00:21 UTCEG score recompute
  5. 2026-07-22 21:59 UTCEG score recompute
  6. 2026-07-22 14:04 UTCEPSS rescore
  7. 2026-07-21 15:21 UTCEPSS rescore
  8. 2026-07-21 15:21 UTCEPSS rescore
  9. 2026-07-20 17:03 UTCEPSS rescore
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  13. 2026-07-16 16:59 UTCEPSS rescore
  14. 2026-07-15 16:54 UTCEPSS rescore
  15. 2026-07-15 16:54 UTCEPSS rescore
  16. 2026-07-15 01:56 UTCEPSS rescore
  17. 2026-07-12 05:42 UTCEPSS rescore
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  24. 2026-07-06 16:24 UTCEPSS rescore
  25. 2026-07-05 02:26 UTCEPSS rescore
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  1. 2026-07-01 15:02 UTCEPSS rescore
  2. 2026-06-30 23:19 UTCEPSS rescore
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  4. 2026-06-29 14:03 UTCEPSS rescore
  5. 2026-06-29 14:03 UTCEPSS rescore
  6. 2026-06-28 04:53 UTCEPSS rescore
  7. 2026-06-27 03:05 UTCEPSS rescore
  8. 2026-06-25 13:47 UTCEPSS rescore
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  10. 2026-06-24 14:02 UTCEPSS rescore
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  12. 2026-06-23 21:30 UTCEPSS rescore
  13. 2026-06-21 14:54 UTCEPSS rescore
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  15. 2026-06-21 01:57 UTCEPSS rescore
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  17. 2026-06-18 17:50 UTCEPSS rescore
  18. 2026-06-17 17:50 UTCEPSS rescore
  19. 2026-06-17 17:49 UTCEPSS rescore
  20. 2026-06-16 17:50 UTCEPSS rescore
  21. 2026-06-16 17:50 UTCEPSS rescore
  22. 2026-06-15 17:45 UTCEPSS rescore
  23. 2026-06-14 23:14 UTCEPSS rescore
  24. 2026-06-13 22:57 UTCEPSS rescore
  25. 2026-06-12 23:09 UTCEPSS rescore
  26. 2026-06-12 23:09 UTCEPSS rescore
  27. 2026-06-11 13:57 UTCEPSS rescore
  28. 2026-06-11 13:57 UTCEPSS rescore
  29. 2026-06-10 22:15 UTCEPSS rescore
  30. 2026-06-10 13:18 UTCEPSS rescore
  31. 2026-06-08 14:14 UTCEPSS rescore
  32. 2026-06-06 13:45 UTCEPSS rescore
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  36. 2026-06-04 13:10 UTCEPSS rescore
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  39. 2026-06-01 13:49 UTCEPSS rescore
  40. 2026-06-01 13:49 UTCEPSS rescore
  41. 2026-05-31 00:14 UTCEPSS rescore
  42. 2026-05-29 13:41 UTCEPSS rescore
  43. 2026-05-28 13:42 UTCEPSS rescore
  44. 2026-05-28 13:42 UTCEPSS rescore
  45. 2026-05-27 13:38 UTCEPSS rescore
  46. 2026-05-27 13:38 UTCEPSS rescore
  47. 2026-05-26 07:16 UTCEPSS rescore
  48. 2026-05-26 07:16 UTCEPSS rescore
  49. 2026-05-24 16:43 UTCEPSS rescore
  50. 2026-05-22 21:15 UTCEPSS rescore
  51. 2026-05-21 22:40 UTCEPSS rescore
  52. 2026-05-20 22:37 UTCEPSS rescore
  53. 2026-05-20 22:37 UTCEPSS rescore
  54. 2026-05-20 11:21 UTCEPSS rescore
  55. 2026-05-20 11:21 UTCEPSS rescore
  56. 2026-05-20 11:21 UTCEPSS rescore
  57. 2026-05-20 10:10 UTCVendor advisory
  58. 2026-05-20 10:10 UTCGHSA enrichment
  59. 2026-05-20 06:02 UTCVendor advisory
  60. 2026-05-20 06:02 UTCGHSA enrichment
  61. 2026-05-20 01:55 UTCVendor advisory
  62. 2026-05-20 01:55 UTCGHSA enrichment
  63. 2026-05-19 21:47 UTCVendor advisory
  64. 2026-05-19 21:47 UTCGHSA enrichment
  65. 2026-05-19 17:40 UTCVendor advisory
  66. 2026-05-19 17:40 UTCGHSA enrichment
  67. 2026-05-19 13:32 UTCVendor advisory
  68. 2026-05-19 13:32 UTCGHSA enrichment
  69. 2026-05-19 09:24 UTCVendor advisory
  70. 2026-05-19 09:24 UTCGHSA enrichment
  71. 2026-05-19 05:16 UTCVendor advisory
  72. 2026-05-19 05:16 UTCGHSA enrichment
  73. 2026-05-19 01:09 UTCEG score recompute
  74. 2026-05-19 01:09 UTCVendor advisory
  75. 2026-05-19 01:09 UTCGHSA enrichment

Publicly available exploits

(2 references)

Working exploit code is in the public domain (1 GitHub PoC) (1 Exploit-DB entry). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCockeghem/CVE-2015-6835-checker
    First seen Dec 19, 2015
    Open source ↗
  • Exploit-DBEDB-38123✓ verified
    First seen Sep 9, 2015

    PHP Session Deserializer - Use-After-Free

    Open source ↗

Related CVEs(same vendor)

Frequently asked(5)

What is CVE-2015-6835?
CVE-2015-6835 is a critical vulnerability published on May 16, 2016. The session deserializer in PHP before 5.4.45, 5.5.x before 5.5.29, and 5.6.x before 5.6.13 mishandles multiple phpvarunserialize calls, which allow remote attackers to execute arbitrary code or cause a denial of service (use-after-free) via crafted session content.
When was CVE-2015-6835 disclosed?
CVE-2015-6835 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-2015-6835 actively exploited?
CVE-2015-6835 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 98.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2015-6835?
CVE-2015-6835 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2015-6835?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2015-6835, 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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