Craft CMS has Twig Function Blocklist Bypass

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.1 · 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/E:U · score source

EPSS

• CVE-2026-28783: 0.51% estimated exploitation activity in the next 30 days; percentile 43.74 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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. Twig has already deprecated this behavior, and it will eventually be removed from Twig altogether. https://github.com/twigphp/Twig/blob/946ddeafa3c9f4ce279d1f34051af041db0e16f2/src/Extension/CoreExtension.php#L2096 This has been resolved in Craft 4.17.0 and 5.9.0, which removes the blocklist and disables all non-Clousure arrow functions in Twig globally via the enableTwigSandbox config setting. That setting is enabled by default…

Published by the source

3 Mar 2026, 21:01 UTC

Last modified by the source

4 Mar 2026, 18:39 UTC

Source last checked

26 Oct 2026, 14:38 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-5fvc-7894-ghp4

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# Patch Next advisory brief: CVE-2026-28783

Advisory: Craft CMS has Twig Function Blocklist Bypass
IDs: CVE-2026-28783, GHSA-5fvc-7894-ghp4
Record: https://patchnext.com/advisories/cve-2026-28783 (revision 1, source checked 26 Oct 2026, 14:38 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: craftcms/cms 5.9.0-beta.1, 4.17.0-beta.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist craftcms/cms: affected >= 5.0.0-RC1, < 5.9.0-beta.1; >= 4.0.0-RC1, < 4.17.0-beta.1; fixed in 5.9.0-beta.1, 4.17.0-beta.1

## Suggested inspection (read-only)
- Packagist craftcms/cms: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on craftcms/cms.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-5fvc-7894-ghp4 (GitHub-reviewed advisory GHSA-5fvc-7894-ghp4 lists affected ranges: Packagist craftcms/cms >=5.0.0-RC1 =4.0.0-RC1 <4.17.0-beta.1)

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