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CVE-2016-5771

37
FAUCET Score

CVE-2016-5771 is a critical use-after-free vulnerability in the SPL extension of PHP versions prior to 5.5.37 and 5.6.23, affecting products like Debian and openSUSE. This flaw allows remote attackers to execute arbitrary code or cause a denial of service through crafted serialized data due to improper interaction with the unserialize implementation and garbage collection. Rated with a CVSS score of 9.8 (CRITICAL), it presents a low-complexity attack vector with no user interaction required, leading to high impact on confidentiality, integrity, and availability. While no public exploit code (Metasploit, Nuclei, ExploitDB) is listed, the vulnerability has garnered significant media attention, including a report of its use in attacks against PornHub, indicating a history of real-world exploitation.

Impacted Technologies

VendorProductVersion(s)CPE
< 5.5.37CPE matchmatch criteria
cpe:2.3:a:php:php:*:*:*:*:*:*:*:*
>= 5.6.0, < 5.6.23CPE matchmatch criteria
cpe:2.3:a:php:php:*:*:*:*:*:*:*:*
>= 7.0.0, < 7.0.8CPE matchmatch criteria
cpe:2.3:a:php:php:*:*:*:*:*:*:*:*
42.1CPE matchmatch criteria
cpe:2.3:o:opensuse:leap:42.1:*:*:*:*:*:*:*
13.2CPE matchmatch criteria
cpe:2.3:o:opensuse:opensuse:13.2:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
15.48%
Probability of exploitation in next 30 days
EPSS Percentile
96.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.1548 is in the 92nd percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (22)

github_advisorypatch availablevia nvd_reference
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 6Fixed in: rh-php56-0:2.3-1.el6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 6Fixed in: rh-php56-php-0:5.6.25-1.el6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 6Fixed in: rh-php56-php-pear-1:1.9.5-4.el6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 6.7 EUSFixed in: rh-php56-0:2.3-1.el6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 6.7 EUSFixed in: rh-php56-php-0:5.6.25-1.el6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 6.7 EUSFixed in: rh-php56-php-pear-1:1.9.5-4.el6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 7Fixed in: rh-php56-0:2.3-1.el7
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 7Fixed in: rh-php56-php-0:5.6.25-1.el7
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 7Fixed in: rh-php56-php-pear-1:1.9.5-4.el7
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 7.2 EUSFixed in: rh-php56-0:2.3-1.el7
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 7.2 EUSFixed in: rh-php56-php-0:5.6.25-1.el7
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 7.2 EUSFixed in: rh-php56-php-pear-1:1.9.5-4.el7
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 7.3 EUSFixed in: rh-php56-0:2.3-1.el7
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 7.3 EUSFixed in: rh-php56-php-0:5.6.25-1.el7
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 7.3 EUSFixed in: rh-php56-php-pear-1:1.9.5-4.el7
View patch
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 5Fixed in: php
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 5Fixed in: php53
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: php
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: php
redhatend of lifevia redhat_api
Product: Red Hat Software CollectionsFixed in: php54-php
redhatend of lifevia redhat_api
Product: Red Hat Software CollectionsFixed in: php55-php

Vendor Advisories (1)

redhatCVE-2016-5771Moderate

php: Use After Free Vulnerability in PHP's GC algorithm and unserialize

Jun 23, 2016

References

github.com / php/php-src/commit/3f627e580acfdaf0595ae3b115b8bec677f203ee
PatchThird Party Advisory
lists.apple.com / archives/security-announce/2016/Sep/msg00006.html
Broken LinkMailing List
lists.opensuse.org / opensuse-security-announce/2016-07/msg00004.html
Mailing ListThird Party Advisory
lists.opensuse.org / opensuse-updates/2016-08/msg00003.html
Mailing ListThird Party Advisory
php.net / ChangeLog-5.php
PatchRelease NotesVendor Advisory
rhn.redhat.com / errata/RHSA-2016-2750.html
Third Party Advisory
bugs.php.net / bug.php
ExploitIssue TrackingVendor Advisory
h20566.www2.hpe.com / portal/site/hpsc/public/kb/docDisplay
Third Party Advisory
support.apple.com / HT207170
Third Party Advisory
debian.org / security/2016/dsa-3618
Third Party Advisory
openwall.com / lists/oss-security/2016/06/23/4
Mailing ListPatchThird Party Advisory
securityfocus.com / bid/91401
Third Party AdvisoryVDB Entry