CVE-2026-28783: Craft has a Twig Function Blocklist Bypass

Severity: critical (CVSS 9.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-04 · updated 2026-06-17
Weakness: CWE-94

Description

Craft is a content management system (CMS). Prior to 5.9.0-beta.1 and 4.17.0-beta.1, Craft CMS implements a blocklist to prevent potentially dangerous PHP functions from being called via Twig non-Closure arrow functions. In order to be able to successfully execute this attack, you need to either have allowAdminChanges enabled on production, or a compromised admin account, or an account with access to the System Messages utility. Several PHP functions are not included in the blocklist, which could allow malicious actors with the required permissions to execute various types of payloads, including RCEs, arbitrary file reads, SSRFs, and SSTIs. This vulnerability is fixed in 5.9.0-beta.1 and 4.17.0-beta.1.

Affected products

craftcms cms: from 4.0.0 (excl.) before 4.17.0; from 5.0.0 (excl.) before 5.9.0; 4.0.0, 4.0.0-rc1, 4.0.0-rc2, 4.0.0-rc3, 5.0.0, 5.0.0-rc1 — fixed in 4.17.0, 5.9.0

How to fix

Upgrade to a fixed version: craftcms cms 4.17.0, 5.9.0. Check the vendor advisory for mitigations.

References

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