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CVE-2017-8923

34
FAUCET Score

CVE-2017-8923 is a critical vulnerability affecting PHP versions through 7.1.5, specifically within the zend_string_extend function. Attackers can exploit this by manipulating string objects to create negative lengths, leading to a denial of service (application crash) or potentially other unspecified impacts. With a CVSS score of 9.8, this vulnerability is easily exploitable over the network with no user interaction, posing a high risk to confidentiality, integrity, and availability. Despite its severity, there is no known active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 7.4.24CPE matchmatch criteria
cpe:2.3:a:php:php:*:*:*:*:*:*:*:*
>= 8.0.0, < 8.0.11CPE matchmatch criteria
cpe:2.3:a:php:php:*:*:*:*:*:*:*:*

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
7.19%
Probability of exploitation in next 30 days
EPSS Percentile
93.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0719 is in the 89th 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

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 (6)

microsoftpatch availablevia msrc
Product: cbl2 php 7.4.14-3 on CBL Mariner 2.0Fixed in: 7.4.14-3
microsoftpatch availablevia msrc
Product: 16917-16823Fixed in: 7.4.14-3
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: php:7.4-8080020230118140634.cc342424
View patch
redhatno patchvia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: php:7.3/php
redhatend of lifevia redhat_api
Product: Red Hat Software CollectionsFixed in: rh-php70-php
redhatend of lifevia redhat_api
Product: Red Hat Software CollectionsFixed in: rh-php73-php

Vendor Advisories (2)

redhatCVE-2017-8923Moderate

php: Overflowing the length of string causes crash

May 12, 2017
microsoft2017-May/CVE-2017-8923Critical

The zend_string_extend function in Zend/zend_string.h in PHP through 7.1.5 does not prevent changes to string objects that result in a negative length, which allows remote attackers to cause a denial of service (application crash) or possibly have unspecified other impact by leveraging a script's use of .= with a long string.

May 9, 2017

References

security.netapp.com / advisory/ntap-20241227-0007
bugs.php.net / bug.php
ExploitIssue TrackingVendor Advisory
securityfocus.com / bid/98518
Third Party AdvisoryVDB Entry