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CVE-2016-4540

33
FAUCET Score

CVE-2016-4540 is a critical denial-of-service vulnerability affecting PHP versions before 5.5.35, 5.6.21, and 7.0.6, specifically within the grapheme_stripos function. This flaw allows remote attackers to trigger an out-of-bounds read via a negative offset, potentially leading to system instability or other unspecified impacts. With a CVSS score of 9.8, it is easily exploitable over the network with low complexity and no user interaction, granting high confidentiality, integrity, and availability impacts. While no public exploit code (Metasploit, Nuclei, ExploitDB) or active exploitation has been confirmed, the vulnerability has garnered significant community discussion, indicating awareness among security researchers.

Impacted Technologies

VendorProductVersion(s)CPE
24CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:24:*:*:*:*:*:*:*
42.1CPE matchmatch criteria
cpe:2.3:o:opensuse:leap:42.1:*:*:*:*:*:*:*
<= 5.5.34CPE matchmatch criteria
cpe:2.3:a:php:php:*:*:*:*:*:*:*:*
5.6.0CPE matchmatch criteria
cpe:2.3:a:php:php:5.6.0:*:*:*:*:*:*:*
5.6.1CPE matchmatch criteria
cpe:2.3:a:php:php:5.6.1:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

9.8CRITICAL

CVSS:3.0/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
3.0

Exploit Intelligence

EPSS Score
6.23%
Probability of exploitation in next 30 days
EPSS Percentile
92.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.0623 is in the 87th percentile among its peer group of 36,835 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

No media coverage found for this CVE.

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 (20)

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: 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-2016-4540Low

php: OOB read in grapheme_stripos and grapheme_strpos when negative offset is used

Apr 20, 2016

References

lists.fedoraproject.org / pipermail/package-announce/2016-May/183736.html
lists.opensuse.org / opensuse-updates/2016-05/msg00086.html
lists.opensuse.org / opensuse-updates/2016-06/msg00027.html
php.net / ChangeLog-5.php
Patch
php.net / ChangeLog-7.php
Patch
rhn.redhat.com / errata/RHSA-2016-2750.html
bugs.php.net / bug.php
Exploit
git.php.net
h20566.www2.hpe.com / portal/site/hpsc/public/kb/docDisplay
h20566.www2.hpe.com / portal/site/hpsc/public/kb/docDisplay
h20566.www2.hpe.com / portal/site/hpsc/public/kb/docDisplay
security.gentoo.org / glsa/201611-22
debian.org / security/2016/dsa-3602
openwall.com / lists/oss-security/2016/05/05/21
securityfocus.com / bid/90172