Code Injection in Smarty - CVE-2021-26120
Published: February 23, 2021 / Updated: July 21, 2026
Vulnerability identifier: #VU50870
CSH Severity: Medium
CVSS v4: 8.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2021-26120
CWE-ID: CWE-94
Exploitation vector: Remote access
Exploit availability:
Public exploit is available
Vulnerability details
The vulnerability allows a remote user to execute arbitrary PHP code on the target system.
The vulnerability exists due to improper input validation when processing data passed via an unexpected function name after a "{function name=" substring. A remote user can send a specially crafted request and execute arbitrary PHP code on the target system.
Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.
Affected software
Smarty
Gentoo Linux
Fedora
Ubuntu
smarty3 (Ubuntu package)
smarty3 (Debian package)
php-Smarty
Gentoo Linux
Fedora
Ubuntu
smarty3 (Ubuntu package)
smarty3 (Debian package)
php-Smarty
How to mitigate CVE-2021-26120
Install updates from vendor's website.
Smarty - update to 3.1.39
smarty3 (Ubuntu package) - addressed in versions 3.1.31+20161214.1.c7d42e4+selfpack1-3ubuntu0.1, 3.1.39-2ubuntu0.21.10.1
smarty3 (Debian package) - addressed in versions 3.1.33+20180830.1.3a78a21f+selfpack1-1+deb10u1, 3.1.39-2+deb11u1
php-Smarty - addressed in versions 3.1.47-1.el7, 3.1.47-1.fc36, 3.1.47-1.fc37
smarty3 (Ubuntu package) - addressed in versions 3.1.31+20161214.1.c7d42e4+selfpack1-3ubuntu0.1, 3.1.39-2ubuntu0.21.10.1
smarty3 (Debian package) - addressed in versions 3.1.33+20180830.1.3a78a21f+selfpack1-1+deb10u1, 3.1.39-2+deb11u1
php-Smarty - addressed in versions 3.1.47-1.el7, 3.1.47-1.fc36, 3.1.47-1.fc37