CVE-2021-27903: Craftcms/cms Craft CMS Remote Code Injection Vulnerability

CRITICAL
Advisory Identifier: GHSA-x2j7-6hxm-87p3
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CVSS 9.8
CWE-94 CWE-74
Published
Advisory Summary

CVE-2021-27903 is a CRITICAL (CVSS 9.8) craft cms remote code injection vulnerability (CWE-94: Improper Control of Generation of Code ('Code Injection')) affecting Craftcms/cms libraries in the Packagist ecosystem. The issue involves craft cms remote code injection. Remediation is available by upgrading affected packages to version 3.6.7.

CVE-2021-27903 at a Glance

CVE Identifier CVE-2021-27903
GHSA Identifier GHSA-x2j7-6hxm-87p3
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-94: Improper Control of Generation of Code ('Code Injection')
Affected Product Craftcms/cms
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 9.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2021-27903

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: 3.6.7 
Upgrade craftcms/cms to 3.6.7
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-2021-27903, 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 3.6.7), 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

An issue was discovered in Craft CMS before 3.6.7. In some circumstances, a potential Remote Code Execution vulnerability existed on sites that did not restrict administrative changes (if an attacker were somehow able to hijack an administrator's session).

CVE-2021-27903 Affected Craftcms/cms Versions

1 component(s)
Fixed Versions:
3.6.7
Product / Package Ecosystem Affected Versions Fixed Version
craftcms/cms
 Packagist
< 3.6.7
3.6.7

References

NVD — CVE-2021-27903 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-27903
Security Fix Commit FIX COMMIT
https://github.com/craftcms/cms/commit/c17728fa0bec11d3b82c34defe0930ed409aec38
Craftcms/cms Source Repository REPOSITORY
https://github.com/craftcms/cms/blob/develop/CHANGELOG.md#367---2021-02-23
Craftcms/cms Source Repository REPOSITORY
https://github.com/craftcms/cms/blob/develop/CHANGELOG.md#security

Frequently Asked Questions

What is CVE-2021-27903?
CVE-2021-27903 is a security vulnerability in Craftcms/cms involving Craft CMS Remote Code Injection under CWE-94: Improper Control of Generation of Code ('Code Injection').
Which Craftcms/cms versions are affected?
Affected versions include releases prior to 3.6.7 across affected packages: craftcms/cms.
What version fixes CVE-2021-27903?
Upgrading to 3.6.7 (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 3.6.7. Upgrade your dependency to 3.6.7 or later.
What is the CVSS score of CVE-2021-27903?
CVE-2021-27903 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2021-27903?
CVE-2021-27903 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-2021-27903?
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-x2j7-6hxm-87p3",
  "modified" : "2023-09-21T19:51:08Z",
  "published" : "2021-07-02T18:36:41Z",
  "aliases" : [ "CVE-2021-27903" ],
  "summary" : "Craft CMS Remote Code Injection",
  "details" : "An issue was discovered in Craft CMS before 3.6.7. In some circumstances, a potential Remote Code Execution vulnerability existed on sites that did not restrict administrative changes (if an attacker were somehow able to hijack an administrator's session).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "craftcms/cms"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.6.7"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-27903"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/commit/c17728fa0bec11d3b82c34defe0930ed409aec38"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/blob/develop/CHANGELOG.md#367---2021-02-23"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/blob/develop/CHANGELOG.md#security"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-74", "CWE-94" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-07-01T21:38:23Z",
    "nvd_published_at" : "2021-06-30T12:15:00Z"
  }
}