CVE-2026-28784: Craftcms/cms Remote Code Execution Vulnerability

MODERATE
Advisory Identifier: GHSA-qc86-q28f-ggww
Share
CWE-1336
Published
Advisory Summary

CVE-2026-28784 is a MODERATE remote code execution vulnerability (CWE-1336: Improper Neutralization of Special Elements Used in a Template Engine) affecting Craftcms/cms libraries in the Packagist ecosystem. The issue involves craft cms has potential authenticated remote code execution via twig ssti. Remediation is available by upgrading affected packages to version 5.9.0-beta.1, 4.17.0-beta.1.

CVE-2026-28784 at a Glance

CVE Identifier CVE-2026-28784
GHSA Identifier GHSA-qc86-q28f-ggww
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-1336: Improper Neutralization of Special Elements Used in a Template Engine
Affected Product Craftcms/cms
Package Ecosystem Packagist
Published Date
Last Updated

How to Fix CVE-2026-28784

To remediate this vulnerability, upgrade all affected Craftcms/cms dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

craftcms/cms fixed: 5.9.0-beta.1 
Upgrade craftcms/cms to 5.9.0-beta.1
craftcms/cms fixed: 4.17.0-beta.1 
Upgrade craftcms/cms to 4.17.0-beta.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for craftcms/cms

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-28784, inspect your project dependencies for Craftcms/cms:

inspect dependencies for craftcms/cms

Analyze the terminal output to locate any version of Craftcms/cms in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.9.0-beta.1), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-1336: Improper Neutralization of Special Elements Used in a Template Engine, where the product uses a template engine to insert or process externally-influenced input, but it does not neutralize or incorrectly neutralizes special elements or syntax that can be interpreted as template expressions or other code directives when processed by the engine. In Craftcms/cms, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

For this to work, the attacker must have administrator access to the Craft Control Panel, and [allowAdminChanges](https://craftcms.com/docs/5.x/reference/config/general.html#allowadminchanges) must be enabled, which is against Craft CMS' recommendations for any non-dev environment. https://craftcms.com/knowledge-base/securing-craft#set-allowAdminChanges-to-false-in-production Alternatively, they can have a non-administrator account with `allowAdminChanges` disabled, but they must have access to the System Messages utility. It is possible to craft a malicious payload using the Twig `map` filter in text fields that accept Twig input under Settings in the Craft control panel or using the System Messages utility, which could lead to a RCE. Users should update to the patched versions (5.8.22 and 4.16.18) to mitigate the issue. References: https://github.com/craftcms/cms/pull/18208

CVE-2026-28784 Affected Craftcms/cms Versions

2 component(s)
Fixed Versions:
5.9.0-beta.14.17.0-beta.1
Product / Package Ecosystem Affected Versions Fixed Version
craftcms/cms
 Packagist
≥ 5.0.0-RC1
< 5.9.0-beta.1
5.9.0-beta.1
craftcms/cms
 Packagist
≥ 4.0.0-RC1
< 4.17.0-beta.1
4.17.0-beta.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/craftcms/cms/security/advisories/GHSA-qc86-q28f-ggww
NVD — CVE-2026-28784 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-28784
Craftcms/cms Source Repository REPOSITORY
https://github.com/craftcms/cms/pull/18208
craftcms.com/knowledge-base/secu... WEB
https://craftcms.com/knowledge-base/securing-craft#set-allowAdminChanges-to-false-in-production
Craftcms/cms Source Repository REPOSITORY
https://github.com/craftcms/cms

Frequently Asked Questions

What is CVE-2026-28784?
CVE-2026-28784 is a security vulnerability in Craftcms/cms involving Craft CMS has potential authenticated Remote Code Execution via Twig SSTI under CWE-1336: Improper Neutralization of Special Elements Used in a Template Engine.
Which Craftcms/cms versions are affected?
Affected versions include releases prior to 5.9.0-beta.1, 4.17.0-beta.1 across affected packages: craftcms/cms.
What version fixes CVE-2026-28784?
Upgrading to 5.9.0-beta.1, 4.17.0-beta.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is craftcms/cms affected?
Yes, craftcms/cms is affected in releases prior to 5.9.0-beta.1, 4.17.0-beta.1. Upgrade your dependency to 5.9.0-beta.1, 4.17.0-beta.1 or later.
What CWE is associated with CVE-2026-28784?
CVE-2026-28784 is classified under CWE-1336: Improper Neutralization of Special Elements Used in a Template Engine (The product uses a template engine to insert or process externally-influenced input, but it does not neutralize or incorrectly neutralizes special elements or syntax that can be interpreted as template expressions or other code directives when processed by the engine.).
How can I check Packagist dependencies for CVE-2026-28784?
Run the dependency tree command: 'inspect dependencies for craftcms/cms'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-qc86-q28f-ggww",
  "modified" : "2026-03-04T18:39:16Z",
  "published" : "2026-03-03T21:06:41Z",
  "aliases" : [ "CVE-2026-28784" ],
  "summary" : "Craft CMS has potential authenticated Remote Code Execution via Twig SSTI",
  "details" : "For this to work, the attacker must have administrator access to the Craft Control Panel, and [allowAdminChanges](https://craftcms.com/docs/5.x/reference/config/general.html#allowadminchanges) must be enabled, which is against Craft CMS' recommendations for any non-dev environment.\n\nhttps://craftcms.com/knowledge-base/securing-craft#set-allowAdminChanges-to-false-in-production\n\nAlternatively, they can have a non-administrator account with `allowAdminChanges` disabled, but they must have access to the System Messages utility.\n\nIt is possible to craft a malicious payload using the Twig `map` filter in text fields that accept Twig input under Settings in the Craft control panel or using the System Messages utility, which could lead to a RCE.\n\nUsers should update to the patched versions (5.8.22 and 4.16.18) to mitigate the issue.\n\nReferences:\n\nhttps://github.com/craftcms/cms/pull/18208",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "craftcms/cms"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "5.0.0-RC1"
      }, {
        "fixed" : "5.9.0-beta.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "craftcms/cms"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0-RC1"
      }, {
        "fixed" : "4.17.0-beta.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/security/advisories/GHSA-qc86-q28f-ggww"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-28784"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/pull/18208"
  }, {
    "type" : "WEB",
    "url" : "https://craftcms.com/knowledge-base/securing-craft#set-allowAdminChanges-to-false-in-production"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/craftcms/cms"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1336" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-03T21:06:41Z",
    "nvd_published_at" : "2026-03-04T17:16:21Z"
  }
}