No exploitation reportedFix available

CVE-2017-8923

Q: Is CVE-2017-8923 actively exploited?

Active exploitation of CVE-2017-8923 has not been confirmed. Its EPSS score was 7.2% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2017-8923?

CVE-2017-8923 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

No exploitation reported by the sources we read.

Published2017-05-12
Fixed in8.0.11 · 7.4.24
WeaknessCWE-787

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC

2017-05-1220:29CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2017-8923?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2017-8923?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

PHP

Branch	Affected	Fixed in	Source
8.0	≥ 8.0.0, < 8.0.11	8.0.11	NVD
7.4	< 7.4.24	7.4.24	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update PHP to 8.0.11 · 7.4.24

Advisories and patches

bugs.php.netVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.19.8read 2026-10-23
NVDCVSS 2.07.5read 2026-10-23
NVDweakness (CWE)CWE-787read 2026-10-23
FIRST EPSSEPSS score7.2 %2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: 2017-05-12
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2017-8923?

Is CVE-2017-8923 actively exploited?

Active exploitation of CVE-2017-8923 has not been confirmed. Its EPSS score was 7.2% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2017-8923?

CVE-2017-8923 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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