Description
In PHP versions 7.3.x below 7.3.16 and 7.4.x below 7.4.4, while using mb_strtolower() function with UTF-32LE encoding, certain invalid strings could cause PHP to overwrite stack-allocated buffer. This could lead to memory corruption, crashes and potentially code execution.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| PHP Group | PHP | 7.3.x – < 7.3.16, 7.4.x – < 7.4.4 | 7.3.16 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 11 | php7.4 | 7.4.5-1 | — |
| Debian 10 | php7.3 | 7.3.19-1~deb10u1 | DSA-4719-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | php7.4 | 7.4.3-4ubuntu1.1 | USN-4330-2 |
| Ubuntu 18.04 LTS | php7.2 | 7.2.24-0ubuntu0.18.04.4 | USN-4330-1 |
| Ubuntu 16.04 LTS | php7.0 | 7.0.33-0ubuntu0.16.04.14 | USN-4330-1 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 14.04 LTS | php5 | 5.5.9+dfsg-1ubuntu4.29+esm11 | USN-4330-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | apcu-panel +2 | 5.1.17-1.module+el8.1.0+3189+a1bff096 | RHSA-2020:3662 |
| RHEL 8 | libzip +2 | 1.5.2-1.module+el8.1.0+3189+a1bff096 | RHSA-2020:3662 |
| RHEL 8 | php +25 | 7.3.20-1.module+el8.2.0+7373+b272fdef | RHSA-2020:3662 |
| RHEL 8 | php-pear | 1:1.10.9-1.module+el8.1.0+3189+a1bff096 | RHSA-2020:3662 |
| RHEL 8 | php-pecl-rrd | 2.0.1-1.module+el8.2.0+4968+1d5097db | RHSA-2020:3662 |
| RHEL 8 | php-pecl-xdebug | 2.8.0-1.module+el8.2.0+4968+1d5097db | RHSA-2020:3662 |
| RHEL 8 | php-pecl-zip | 1.15.4-1.module+el8.1.0+3189+a1bff096 | RHSA-2020:3662 |
| RHEL 3 | rh-php73-php +27 | 7.3.20-1.el7 | RHSA-2020:5275 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 8 | apcu-panel +2 | 5.1.17-1.module_el8.3.0+2009+b272fdef | ALSA-2020:3662 |
| AlmaLinux 8 | libzip +2 | 1.5.2-1.module_el8.3.0+2009+b272fdef | ALSA-2020:3662 |
| AlmaLinux 8 | php +25 | 7.3.20-1.module_el8.3.0+2009+b272fdef | ALSA-2020:3662 |
| AlmaLinux 8 | php-pear | 1:1.10.9-1.module_el8.3.0+2009+b272fdef | ALSA-2020:3662 |
| AlmaLinux 8 | php-pecl-rrd | 2.0.1-1.module_el8.3.0+2009+b272fdef | ALSA-2020:3662 |
| AlmaLinux 8 | php-pecl-xdebug | 2.8.0-1.module_el8.3.0+2009+b272fdef | ALSA-2020:3662 |
| AlmaLinux 8 | php-pecl-zip | 1.15.4-1.module_el8.3.0+2009+b272fdef | ALSA-2020:3662 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | libzip | 1.5.2-1.module+el8.4.0+414+2e7afcdd | RLSA-2020:3662 |
| Rocky Linux 8 | php | 7.3.20-1.module+el8.4.0+414+2e7afcdd | RLSA-2020:3662 |
| Rocky Linux 8 | php-pear | 1:1.10.9-1.module+el8.4.0+414+2e7afcdd | RLSA-2020:3662 |
| Rocky Linux 8 | php-pecl-apcu | 5.1.17-1.module+el8.4.0+414+2e7afcdd | RLSA-2020:3662 |
| Rocky Linux 8 | php-pecl-rrd | 2.0.1-1.module+el8.4.0+414+2e7afcdd | RLSA-2020:3662 |
| Rocky Linux 8 | php-pecl-xdebug | 2.8.0-1.module+el8.4.0+414+2e7afcdd | RLSA-2020:3662 |
| Rocky Linux 8 | php-pecl-zip | 1.15.4-1.module+el8.4.0+414+2e7afcdd | RLSA-2020:3662 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.15 | php7 | 7.3.16-r0 | — |
| Alpine v3.14 | php7 | 7.3.16-r0 | — |
| Alpine v3.13 | php7 | 7.3.16-r0 | — |
| Alpine v3.12 | php7 | 7.3.16-r0 | — |
| Alpine v3.11 | php7 | 7.3.16-r0 | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | apcu-panel +2 | 5.1.17-1.module+el8.2.0+5569+98c8b30d | ELSA-2020-3662 |
| Oracle Linux 8 | libzip +2 | 1.5.2-1.module+el8.2.0+5569+98c8b30d | ELSA-2020-3662 |
| Oracle Linux 8 | php +25 | 7.3.20-1.module+el8.2.0+7784+4033621d | ELSA-2020-3662 |
| Oracle Linux 8 | php-pear | 1:1.10.9-1.module+el8.2.0+5569+98c8b30d | ELSA-2020-3662 |
| Oracle Linux 8 | php-pecl-rrd | 2.0.1-1.module+el8.2.0+5569+98c8b30d | ELSA-2020-3662 |
| Oracle Linux 8 | php-pecl-xdebug | 2.8.0-1.module+el8.2.0+5569+98c8b30d | ELSA-2020-3662 |
| Oracle Linux 8 | php-pecl-zip | 1.15.4-1.module+el8.2.0+5569+98c8b30d | ELSA-2020-3662 |
Advisories 11
- ALSA-2020:3662 Moderate: php:7.3 security, bug fix, and enhancement update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2020:3662 Red Hat Security Advisory: php:7.3 security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Aug 18, 2026
- RHSA-2020:5275 Red Hat Security Advisory: rh-php73-php security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Aug 18, 2026
- USN-4330-2 php7.4 vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- USN-4330-1 php5, php7.0, php7.2, php7.3 vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- DSA-4719-1 php7.3 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RLSA-2020:3662 Moderate: php:7.3 security, bug fix, and enhancement update Rocky Linux Security Advisories · Feb 4, 2026
- FSA-202302 Festo: Several vulnerabilities in FactoryViews CERT@VDE · Feb 2, 2026
- ICSA-26-027-02 Festo Didactic SE MES PC CISA ICS & IT advisories · Jan 27, 2026
- FSA-202402 Several Vulnerabilities in MES PC (Windows 10) CERT@VDE · Dec 8, 2025
- ELSA-2020-3662 Moderate: php:7.3 security, bug fix, and enhancement update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Sep 9, 2020
References
- USN-4330-1 vendor-advisory
- USN-4330-2 vendor-advisory
- DSA-4719 vendor-advisory
- https://security.netapp.com/advisory/ntap-20200403-0001/
- https://www.oracle.com/security-alerts/cpuoct2021.html
- https://bugs.php.net/bug.php?id=79371
- https://www.php.net/ChangeLog-7.php#7.4.4
- https://www.tenable.com/security/tns-2021-14