What’s Vulnerable › Vulnerabilities

CVE-2021-29454: Sandbox Escape by math function in smarty

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.8% 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-74

Description

Smarty is a template engine for PHP, facilitating the separation of presentation (HTML/CSS) from application logic. Prior to versions 3.1.42 and 4.0.2, template authors could run arbitrary PHP code by crafting a malicious math string. If a math string was passed through as user provided data to the math function, external users could run arbitrary PHP code by crafting a malicious math string. Users should upgrade to version 3.1.42 or 4.0.2 to receive a patch.

Affected products

• Debian Linux: 9.0, 10.0, 11.0
• Fedoraproject Fedora: 36, 37
• Smarty: before 3.1.42; from 4.0.0 before 4.0.2 — fixed in 3.1.42, 4.0.2

How to fix

Upgrade to a fixed version: Smarty 3.1.42, 4.0.2. Check the vendor advisory for mitigations.

References

• https://github.com/smarty-php/smarty/commit/215d81a9fa3cd63d82fb3ab56ecaf97cf1e7db71
• https://github.com/smarty-php/smarty/releases/tag/v3.1.42
• https://github.com/smarty-php/smarty/releases/tag/v4.0.2
• https://github.com/smarty-php/smarty/security/advisories/GHSA-29gp-2c3m-3j6m
• 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://packagist.org/packages/smarty/smarty
• https://security.gentoo.org/glsa/202209-09
• https://www.debian.org/security/2022/dsa-5151
• https://www.smarty.net/docs/en/language.function.math.tpl
• https://github.com/smarty-php/smarty/commit/215d81a9fa3cd63d82fb3ab56ecaf97cf1e7db71

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