CVE-2015-6835PHP Use-After-Free
php: use-after-free vulnerability in session deserializer
Published Aug 9, 2015 · Updated Apr 22, 2026 · Also known as UBUNTU-CVE-2015-6835
Key Facts
Patch immediately- CVE-2015-6835 is a critical-severity vulnerability (CVSS 9.8 v3.1) affecting PHP, php5 (debian), php54-bcmath (amazon) and 22 more products.
- It is not listed in any known-exploited vulnerabilities catalog. A public exploit is reported by tracking sources, but no code link is listed yet.
- EPSS estimates a 36% probability of exploitation in the next 30 days.
- Fixed versions are available, including apache2-mod_php5 5.5.14-36.1, PHP 5.4.44, php5 5.4.45-0+deb7u1.
- Brandefense priority: patch immediately, because public exploit code exists for a high-severity flaw.
Scores
CVSS v3.1
9.8
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
36%
Higher than 98.4% of all scored CVEs
Exploit maturity
Weaponized
ATLAS score
62/100
Publication score, see How it works
Exploitation Verdict
KEV listed
Not listed
Federal due date
None
No federal due date
Ransomware use
Not reported
Attributed actors
None named
Exploit & Defence Guidance
Exploit maturity
Weaponized
Public exploit code
2
Proof-of-concept links
In-the-wild evidence
0
Reports of active use
Advisories And Exploit References
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.
Affected Products
211 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| PHPPHP | 5.5.0, 5.5.0-alpha1, 5.5.0-alpha2, 5.5.0-alpha3, 5.5.0-alpha4, 5.5.0-alpha5, 5.5.0-alpha6, 5.5.0-beta1 | 5.4.44 |
| php5debian | See advisory | 5.4.45-0+deb7u1 |
| php54-bcmathamazon | See advisory | 5.4.45-1.75.amzn1 |
| php54-cliamazon | See advisory | 5.4.45-1.75.amzn1 |
| php54-commonamazon | See advisory | 5.4.45-1.75.amzn1 |
Patched Releases
apache2-mod_php5
5.5.14-36.1
PHP
5.4.44
php5
5.4.45-0+deb7u1, 5.5.14-36.1, 5.5.9+dfsg-1ubuntu4.13, 5.6.13+dfsg-0+deb8u1
php5-bcmath
5.5.14-36.1
php5-bz2
5.5.14-36.1
php5-calendar
5.5.14-36.1
php5-ctype
5.5.14-36.1
php5-curl
5.5.14-36.1
php5-dba
5.5.14-36.1
php5-devel
5.5.14-36.1
php5-dom
5.5.14-36.1
php5-enchant
5.5.14-36.1
php5-exif
5.5.14-36.1
php5-fastcgi
5.5.14-36.1
php5-fileinfo
5.5.14-36.1
php5-fpm
5.5.14-36.1
php5-ftp
5.5.14-36.1
php5-gd
5.5.14-36.1
php5-gettext
5.5.14-36.1
php5-gmp
5.5.14-36.1
php5-iconv
5.5.14-36.1
php5-intl
5.5.14-36.1
php5-json
5.5.14-36.1
php5-ldap
5.5.14-36.1
php5-mbstring
5.5.14-36.1
Timeline
Publicly disclosed
Aug 9, 2015
Last updated
Apr 22, 2026
Weakness Type
- CWE-416 Use After Free
References
- advisoryubuntu.com · CVE-2015-6835
- advisorycve.org · CVERecord
- advisoryRHSA-2016:0457
- advisorybugzilla.suse.com · 935074
- advisorybugzilla.suse.com · 942291
FAQ
Common Questions.
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.
Affected: PHP versions 5.5.0, 5.5.0-alpha1, 5.5.0-alpha2, 5.5.0-alpha3, 5.5.0-alpha4, 5.5.0-alpha5, 5.5.0-alpha6, 5.5.0-beta1; php5 (debian); php54-bcmath (amazon), among others. The full list is in the CVE brief.
It is not listed in any known-exploited vulnerabilities catalog.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
A public exploit is reported by tracking sources, but no code link is listed yet.
Fixed versions are available, including apache2-mod_php5 5.5.14-36.1, PHP 5.4.44, php5 5.4.45-0+deb7u1.
Brandefense priority: patch immediately, because public exploit code exists for a high-severity flaw.
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