CVE-2026-31857: Craftcms/cms Remote Code Execution Vulnerability

HIGH
Advisory Identifier: GHSA-fp5j-j7j4-mcxc
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CWE-94
Published
Advisory Summary

CVE-2026-31857 is a HIGH remote code execution vulnerability (CWE-94: Improper Control of Generation of Code ('Code Injection')) affecting Craftcms/cms libraries in the Packagist ecosystem. The issue involves craftcms has an rce vulnerability via relational conditionals in the control panel. Remediation is available by upgrading affected packages to version 5.9.9, 4.17.4.

CVE-2026-31857 at a Glance

CVE Identifier CVE-2026-31857
GHSA Identifier GHSA-fp5j-j7j4-mcxc
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-94: Improper Control of Generation of Code ('Code Injection')
Affected Product Craftcms/cms
Package Ecosystem Packagist
Published Date
Last Updated

How to Fix CVE-2026-31857

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: 5.9.9 
Upgrade craftcms/cms to 5.9.9
craftcms/cms fixed: 4.17.4 
Upgrade craftcms/cms to 4.17.4
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-2026-31857, 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 5.9.9), 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-94: Improper Control of Generation of Code ('Code Injection'), where the product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. 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

A Remote Code Execution vulnerability exists in the Craft CMS 5 conditions system. The `BaseElementSelectConditionRule::getElementIds()` method passes user-controlled string input through `renderObjectTemplate()` -- an unsandboxed Twig rendering function with escaping disabled. Any authenticated Control Panel user (including non-admin roles such as Author or Editor) can achieve full RCE by sending a crafted condition rule via standard element listing endpoints. This vulnerability requires no admin privileges, no special permissions beyond basic control panel access, and bypasses all production hardening settings (allowAdminChanges: false, devMode: false, enableTwigSandbox: true). Users should update to the patched 5.99 release to mitigate the issue.

CVE-2026-31857 Affected Craftcms/cms Versions

2 component(s)
Fixed Versions:
5.9.94.17.4
Product / Package Ecosystem Affected Versions Fixed Version
craftcms/cms
 Packagist
≥ 5.0.0-RC1
< 5.9.9
5.9.9
craftcms/cms
 Packagist
≥ 4.0.0-beta.1
< 4.17.4
4.17.4

References

GitHub Advisory / Wiki ADVISORY
https://github.com/craftcms/cms/security/advisories/GHSA-fp5j-j7j4-mcxc
NVD — CVE-2026-31857 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-31857
Security Fix Commit FIX COMMIT
https://github.com/craftcms/cms/commit/8d4903647dcfd31b8d40ed027e27082013347a80
Craftcms/cms Source Repository REPOSITORY
https://github.com/craftcms/cms

Frequently Asked Questions

What is CVE-2026-31857?
CVE-2026-31857 is a security vulnerability in Craftcms/cms involving CraftCMS has an RCE vulnerability via relational conditionals in the control panel under CWE-94: Improper Control of Generation of Code ('Code Injection').
Which Craftcms/cms versions are affected?
Affected versions include releases prior to 5.9.9, 4.17.4 across affected packages: craftcms/cms.
What version fixes CVE-2026-31857?
Upgrading to 5.9.9, 4.17.4 (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 5.9.9, 4.17.4. Upgrade your dependency to 5.9.9, 4.17.4 or later.
What CWE is associated with CVE-2026-31857?
CVE-2026-31857 is classified under CWE-94: Improper Control of Generation of Code ('Code Injection') (The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.).
How can I check Packagist dependencies for CVE-2026-31857?
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-fp5j-j7j4-mcxc",
  "modified" : "2026-03-11T20:44:40Z",
  "published" : "2026-03-11T14:56:45Z",
  "aliases" : [ "CVE-2026-31857" ],
  "summary" : "CraftCMS has an RCE vulnerability via relational conditionals in the control panel",
  "details" : "A Remote Code Execution vulnerability exists in the Craft CMS 5 conditions system.\n\nThe `BaseElementSelectConditionRule::getElementIds()` method passes user-controlled string input\nthrough `renderObjectTemplate()` -- an unsandboxed Twig rendering function with escaping disabled.\n\nAny authenticated Control Panel user (including non-admin roles such as Author or Editor) can achieve full\nRCE by sending a crafted condition rule via standard element listing endpoints.\n\nThis vulnerability requires no admin privileges, no special permissions beyond basic control panel access, and\nbypasses all production hardening settings (allowAdminChanges: false, devMode: false,\nenableTwigSandbox: true).\n\nUsers should update to the patched 5.99 release to mitigate the issue.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/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" : "5.9.9"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 5.9.8"
    }
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "craftcms/cms"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0-beta.1"
      }, {
        "fixed" : "4.17.4"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.17.3"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/security/advisories/GHSA-fp5j-j7j4-mcxc"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-31857"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/commit/8d4903647dcfd31b8d40ed027e27082013347a80"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/craftcms/cms"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-94" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-11T14:56:45Z",
    "nvd_published_at" : "2026-03-11T18:16:24Z"
  }
}