What is CVE-2016-5768?

CVE-2016-5768 is a critical-severity vulnerability in PHP, classified under Double Free. CVSS score: 9.8/10. Published 2016-08-07.

How severe is CVE-2016-5768?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2016-5768 known to be exploited?

3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Double Free in PHP

CVE-2016-5768

Double free vulnerability in the _php_mb_regex_ereg_replace_exec function in php_mbregex.c in the mbstring extension in PHP before 5.5.37, 5.6.x before 5.6.23, and 7.x before 7.0.8 allows remote attackers to execute arbitrary code or cause a denial of service (application crash) by leveraging a callback exception.

Vulnerability class: Double Free

Published 2016-08-07 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.096 (95.3th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 95th percentile — 95.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.096 · newest: 0.096 · change: 0.000

Affected products

PHP — versions 5.6.0, 5.6.1, 5.6.2

Weakness classification (CWE)

CWE-415 — Double Free

Public proof-of-concept exploits

References

lists.apple.com/archives/security-announce/2016/Sep/msg00006.html (vendor-advisory)
lists.opensuse.org/opensuse-security-announce/2016-07/msg00004.html (vendor-advisory)
lists.opensuse.org/opensuse-updates/2016-08/msg00003.html (vendor-advisory)
rhn.redhat.com/errata/RHSA-2016-2750.html (vendor-advisory)
rhn.redhat.com/errata/RHSA-2016-2598.html (vendor-advisory)
php.net/ChangeLog-5.php (Patch, Release Notes)
bugs.php.net/bug.php (Exploit, Vendor Advisory)
github.com/php/php-src/commit/5b597a2e5b28e2d5a52fc1be13f425f08f47cb62
www.openwall.com/lists/oss-security/2016/06/23/4 (mailing-list, Release Notes)
www.debian.org/security/2016/dsa-3618 (vendor-advisory)

Frequently asked questions

What is CVE-2016-5768?: CVE-2016-5768 is a critical-severity vulnerability in PHP, classified under Double Free. CVSS score: 9.8/10. Published 2016-08-07.
How severe is CVE-2016-5768?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2016-5768 known to be exploited?: 3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.