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Fencer Intel
critical 9.8

CVE-2015-6835 in the critical feed json

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,…

published 10y ago modified 4mo ago also EUVD-2015-6771

cvss
9.8
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
36.2%
EPSS 36.2% chance of exploitation in 30 days, percentile 98%
public exploits
1
Exploit-DB

Summary

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.

Patch / fix

  • php5 Ubuntu 14.04 LTS 5.5.9+dfsg-1ubuntu4.13

ubuntu advisories UBUNTU-CVE-2015-6835

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • rh-php56-php RHEL 2 SOFTWARE_COLLECTIONS 5.6.5-8.el6
  • rh-php56-php RHEL 2 SOFTWARE_COLLECTIONS 5.6.5-8.el7
  • rh-php56-php-gd RHEL 2 SOFTWARE_COLLECTIONS 5.6.5-8.el6
  • rh-php56-php-gd RHEL 2 SOFTWARE_COLLECTIONS 5.6.5-8.el7
  • rh-php56-php-cli RHEL 2 SOFTWARE_COLLECTIONS 5.6.5-8.el6
  • rh-php56-php-cli RHEL 2 SOFTWARE_COLLECTIONS 5.6.5-8.el7
  • rh-php56-php-dba RHEL 2 SOFTWARE_COLLECTIONS 5.6.5-8.el6
  • rh-php56-php-dba RHEL 2 SOFTWARE_COLLECTIONS 5.6.5-8.el7

red hat advisories RHSA-2016:0457

  • php5 SLE Software Development Kit 12, SLE Module for Web and Scripting 12 5.5.14-36.1

suse advisories SUSE-SU-2015:1633-1

Is CVE-2015-6835 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2015-6835 updated cvss 5.1

php: use-after-free vulnerability in session deserializer

  • Red Hat Enterprise Linux 5 php, php53 Red Hat Enterprise Linux 6 php, php-gd, php-cli, php-dba, php-fpm, php-pdo, +20 more Red Hat Enterprise Linux 7 php, php-gd, php-cli, php-dba, php-fpm, php-pdo, +18 more Red Hat Software Collections php54-php, php55-php, php54-php-gd, php55-php-gd, php54-php-cli, php54-php-dba, +44 more
    affected: no fix planned “Will not fix”
  • Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 6) rh-php56-php 5.6.5-8.el6, rh-php56-php-gd 5.6.5-8.el6, rh-php56-php-cli 5.6.5-8.el6, rh-php56-php-dba 5.6.5-8.el6, rh-php56-php-dbg 5.6.5-8.el6, rh-php56-php-fpm 5.6.5-8.el6, +22 more Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 7) rh-php56-php 5.6.5-8.el7, rh-php56-php-gd 5.6.5-8.el7, rh-php56-php-cli 5.6.5-8.el7, rh-php56-php-dba 5.6.5-8.el7, rh-php56-php-dbg 5.6.5-8.el7, rh-php56-php-fpm 5.6.5-8.el7, +20 more Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 6.6) rh-php56-php 5.6.5-8.el6, rh-php56-php-gd 5.6.5-8.el6, rh-php56-php-cli 5.6.5-8.el6, rh-php56-php-dba 5.6.5-8.el6, rh-php56-php-dbg 5.6.5-8.el6, rh-php56-php-fpm 5.6.5-8.el6, +22 more Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 6.7) rh-php56-php 5.6.5-8.el6, rh-php56-php-gd 5.6.5-8.el6, rh-php56-php-cli 5.6.5-8.el6, rh-php56-php-dba 5.6.5-8.el6, rh-php56-php-dbg 5.6.5-8.el6, rh-php56-php-fpm 5.6.5-8.el6, +22 more Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.1) rh-php56-php 5.6.5-8.el7, rh-php56-php-gd 5.6.5-8.el7, rh-php56-php-cli 5.6.5-8.el7, rh-php56-php-dba 5.6.5-8.el7, rh-php56-php-dbg 5.6.5-8.el7, rh-php56-php-fpm 5.6.5-8.el7, +20 more Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.2) rh-php56-php 5.6.5-8.el7, rh-php56-php-gd 5.6.5-8.el7, rh-php56-php-cli 5.6.5-8.el7, rh-php56-php-dba 5.6.5-8.el7, rh-php56-php-dbg 5.6.5-8.el7, rh-php56-php-fpm 5.6.5-8.el7, +20 more
    +2 more products
    Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 6) rh-php56-php 5.6.5-8.el6, rh-php56-php-gd 5.6.5-8.el6, rh-php56-php-cli 5.6.5-8.el6, rh-php56-php-dba 5.6.5-8.el6, rh-php56-php-dbg 5.6.5-8.el6, rh-php56-php-fpm 5.6.5-8.el6, +22 more Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 7) rh-php56-php 5.6.5-8.el7, rh-php56-php-gd 5.6.5-8.el7, rh-php56-php-cli 5.6.5-8.el7, rh-php56-php-dba 5.6.5-8.el7, rh-php56-php-dbg 5.6.5-8.el7, rh-php56-php-fpm 5.6.5-8.el7, +20 more
    fixed: vendor fix RHSA-2016:0457

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Timeline

  1. First public exploit (EDB-38123)
  2. Published

Exploit prediction

36.16% chance of exploitation in the next 30 days, higher than 98% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • EDB-38123 PHP Session Deserializer - Use-After-Free dos, 2015-09-09

CVSS scores

assigned by version score vector
NVD 3.0 9.8 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Classification

Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.