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Fencer Vulns
critical 9.8

CVE-2017-8923 in the critical feed json

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 nega…

published 2017-05-12 9 y ago modified 2026-06-17 4 mo ago also EUVD-2017-17863

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
7.2%
EPSS 7.2% chance of exploitation in 30 days, percentile 94%
public exploits
0
none known

Summary

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.

Patch / fix

  • php php 7.4.24, 8.0.11
  • php7.2 Ubuntu 18.04 LTS 7.2.24-0ubuntu0.18.04.11
  • php7.4 Ubuntu 20.04 LTS 7.4.3-4ubuntu2.10
  • php7.0 Ubuntu Pro 16.04 LTS 7.0.33-0ubuntu0.16.04.16+esm3

ubuntu advisories UBUNTU-CVE-2017-8923

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • php RHEL 8 7.4.33-1.module+el8.8.0+17865+ef7eddfa
  • libzip RHEL 8 1.6.1-1.module+el8.3.0+6678+b09f589e
  • php-gd RHEL 8 7.4.33-1.module+el8.8.0+17865+ef7eddfa
  • php-cli RHEL 8 7.4.33-1.module+el8.8.0+17865+ef7eddfa
  • php-dba RHEL 8 7.4.33-1.module+el8.8.0+17865+ef7eddfa
  • php-dbg RHEL 8 7.4.33-1.module+el8.8.0+17865+ef7eddfa
  • php-ffi RHEL 8 7.4.33-1.module+el8.8.0+17865+ef7eddfa
  • php-fpm RHEL 8 7.4.33-1.module+el8.8.0+17865+ef7eddfa

red hat advisories RHSA-2023:2903

  • php7 SLES for SAP 15 SP2, SLES 15 SP2-LTSS, SLES 15 SP2-BCL +10 more 7.4.33-150200.3.46.2
  • php7-test openSUSE Leap 15.3 7.4.33-150200.3.46.2
  • php74 SLE Software Development Kit 12 SP5, SLE Module for Web and Scripting 12 7.4.33-1.47.2
  • php7 SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +8 more 7.2.34-150000.4.103.1
  • php7 SLE Module for Web and Scripting 15 SP3, SLE Module for Package Hub 15 SP3 7.4.6-3.32.1
  • php7 SLES for SAP 15 SP1, SLES for SAP 15, SLES 15-LTSS +7 more 7.2.5-4.89.4
  • php72 SLE Software Development Kit 12 SP5, SLE Module for Web and Scripting 12 7.2.5-1.75.1
  • php74 SLE Software Development Kit 12 SP5, SLE Module for Web and Scripting 12 7.4.6-1.33.1

suse advisories SUSE-SU-2022:4069-1SUSE-SU-2022:4068-1SUSE-SU-2022:4067-1SUSE-SU-2022:0699-1SUSE-SU-2022:0679-1SUSE-SU-2022:0577-1

  • php7 openSUSE Leap 15.3 7.4.6-3.32.1
  • php7-test openSUSE Leap 15.3 7.4.6-3.32.1

opensuse advisories openSUSE-SU-2022:0699-1

  • php AlmaLinux 8 7.4.33-1.module_el8.8.0+3477+f828cbb0
  • libzip AlmaLinux 8 1.6.1-1.module_el8.6.0+2750+78feabcb
  • libzip AlmaLinux 8 1.6.1-1.module_el8.6.0+3239+bedf0508
  • php-gd AlmaLinux 8 7.4.33-1.module_el8.8.0+3477+f828cbb0
  • php-cli AlmaLinux 8 7.4.33-1.module_el8.8.0+3477+f828cbb0
  • php-dba AlmaLinux 8 7.4.33-1.module_el8.8.0+3477+f828cbb0
  • php-dbg AlmaLinux 8 7.4.33-1.module_el8.8.0+3477+f828cbb0
  • php-ffi AlmaLinux 8 7.4.33-1.module_el8.8.0+3477+f828cbb0

almalinux advisories ALSA-2023:2903

  • php Rocky Linux 8 7.4.33-1.module+el8.10.0+1604+6558efc7
  • libzip Rocky Linux 8 1.6.1-1.module+el8.10.0+1912+72767185
  • libzip Rocky Linux 8 1.6.1-1.module+el8.10.0+1604+6558efc7
  • php-pear Rocky Linux 8 1:1.10.13-1.module+el8.10.0+1605+02e07af7
  • php-pear Rocky Linux 8 1:1.10.13-1.module+el8.10.0+1912+72767185
  • php-pear Rocky Linux 8 1:1.10.13-1.module+el8.10.0+1604+6558efc7
  • php-pecl-rrd Rocky Linux 8 2.0.1-1.module+el8.10.0+1604+6558efc7
  • php-pecl-rrd Rocky Linux 8 2.0.1-1.module+el8.10.0+1912+72767185

rocky linux advisories RLSA-2023:2903

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2017-8923 updated cvss 7.5

php: Overflowing the length of string causes crash

  • Red Hat Enterprise Linux 8 php, libzip, php-gd, php-cli, php-dba, php-dbg, +30 more
    affected: no fix available
  • Red Hat Software Collections rh-php70-php, rh-php73-php, rh-php70-php-gd, rh-php73-php-gd, rh-php70-php-cli, rh-php70-php-dba, +52 more
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise Linux AppStream (v. 8) php 7.4.33-1.module+el8.8.0+17865+ef7eddfa, libzip 1.6.1-1.module+el8.3.0+6678+b09f589e, php-gd 7.4.33-1.module+el8.8.0+17865+ef7eddfa, php-cli 7.4.33-1.module+el8.8.0+17865+ef7eddfa, php-dba 7.4.33-1.module+el8.8.0+17865+ef7eddfa, php-dbg 7.4.33-1.module+el8.8.0+17865+ef7eddfa, +28 more
    fixed: vendor fix RHSA-2023:2903
  • Red Hat Enterprise Linux 5 php, php53 Red Hat Enterprise Linux 6 php, php-gd, php-cli, php-dba, php-fpm, php-pdo, +20 more Red Hat Enterprise Linux 7 php, php-gd, php-cli, php-dba, php-fpm, php-pdo, +18 more Red Hat Software Collections rh-php56-php, rh-php56-php-gd, rh-php56-php-cli, rh-php56-php-dba, rh-php56-php-dbg, rh-php56-php-fpm, +22 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-24-102-04 updated cvss 9.8

Siemens RUGGEDCOM APE1808

  • Siemens RUGGEDCOM APE1808
    affected: vendor fix

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

Exploit prediction

7.19% chance of exploitation in the next 30 days, higher than 94% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • bugs.php.net https://bugs.php.net/bug.php?id=74577 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.