CVE-2017-8923

Name: CVE-2017-8923
Creator: NVD / NIST
Published: 2017-05-12T20:29:00.5+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 7.19%

Last modified Jun 17, 2026

CVE-2017-8923 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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.. EPSS estimates a 7.19% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

7.19%

93.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-787

Affected Software

Vendor	Product	Versions
Php	Php	< 7.4.24
Php	Php	>= 8.0.0, < 8.0.11

References

http://www.securityfocus.com/bid/98518Third Party Advisory, VDB Entry
https://bugs.php.net/bug.php?id=74577Exploit, Issue Tracking, Vendor Advisory
http://www.securityfocus.com/bid/98518Third Party Advisory, VDB Entry
https://bugs.php.net/bug.php?id=74577Exploit, Issue Tracking, Vendor Advisory
https://security.netapp.com/advisory/ntap-20241227-0007/

Timeline

Published: May 12, 2017
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2017-8923?

How severe is CVE-2017-8923?

CVE-2017-8923 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 7.19% probability of exploitation in the next 30 days.

How do I fix CVE-2017-8923?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2017-8923?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST