CVE-2021-21408: Access to restricted PHP code by dynamic static class access in smarty

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2022-01-10 · updated 2026-06-17
Weakness: CWE-20

Description

Smarty is a template engine for PHP, facilitating the separation of presentation (HTML/CSS) from application logic. Prior to versions 3.1.43 and 4.0.3, template authors could run restricted static php methods. Users should upgrade to version 3.1.43 or 4.0.3 to receive a patch.

Affected products

Debian Linux: 9.0, 10.0, 11.0
Fedoraproject Fedora: 36, 37
Smarty: before 3.1.43; from 4.0.0 before 4.0.3 — fixed in 3.1.43, 4.0.3

How to fix

Upgrade to a fixed version: Smarty 3.1.43, 4.0.3. Check the vendor advisory for mitigations.

References

https://github.com/smarty-php/smarty/commit/19ae410bf56007a5ef24441cdc6414619cfaf664
https://github.com/smarty-php/smarty/releases/tag/v3.1.43
https://github.com/smarty-php/smarty/releases/tag/v4.0.3
https://github.com/smarty-php/smarty/security/advisories/GHSA-4h9c-v5vg-5m6m
https://lists.debian.org/debian-lts-announce/2022/05/msg00005.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BRAJVDRGCIY5UZ2PQHKDTT7RMKG6WJQQ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L777JIBIWJV34HS7LXPIDWASG7TT4LNI/
https://security.gentoo.org/glsa/202209-09
https://www.debian.org/security/2022/dsa-5151
https://github.com/smarty-php/smarty/commit/19ae410bf56007a5ef24441cdc6414619cfaf664
https://github.com/smarty-php/smarty/releases/tag/v3.1.43
https://github.com/smarty-php/smarty/releases/tag/v4.0.3

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