Public proof of concept

CVE-2015-6835

A public proof of concept exists; no exploitation attested.

Published2016-05-16

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC

2016-05-1610:59CVE publishedNVD
2026-10-2319:23First public proof of conceptPoC-in-GitHub
2026-10-2319:23EPSS crossed 10 %FIRST EPSS

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2015-6835?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2015-6835?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

PHP

Branch	Affected	Fixed in	Source
5.6	= 5.6.0	no fix published	NVD
5.6	= 5.6.1	no fix published	NVD
5.6	= 5.6.2	no fix published	NVD
5.6	= 5.6.3	no fix published	NVD
5.6	= 5.6.4	no fix published	NVD
5.6	= 5.6.5	no fix published	NVD
5.6	= 5.6.6	no fix published	NVD
5.6	= 5.6.7	no fix published	NVD
5.6	= 5.6.8	no fix published	NVD
5.6	= 5.6.9	no fix published	NVD
5.6	= 5.6.10	no fix published	NVD
5.6	= 5.6.11	no fix published	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

No fix published by the sources we read yet. NVD record

Detection

read 2026-10-23 19:23 UTC

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: 1 repository, unverifiedockeghem/CVE-2015-6835-checker

Sources

NVDCVSS 3.09.8read 2026-10-23
NVDCVSS 2.07.5read 2026-10-23
FIRST EPSSEPSS score36.2 %read 2026-10-23
PoC-in-GitHubproof of concept1read 2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: 2016-05-16
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2015-6835?

Is CVE-2015-6835 actively exploited?

Active exploitation of CVE-2015-6835 has not been confirmed. Its EPSS score was 36.2% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2015-6835?

CVE-2015-6835 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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