CVE-2019-5420: Railties Remote Code Execution Vulnerability

CRITICAL
Advisory Identifier: GHSA-m42h-mh85-4qgc
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CVSS 9.8
CWE-330 CWE-77
Published
Advisory Summary

CVE-2019-5420 is a CRITICAL (CVSS 9.8) remote code execution vulnerability (CWE-330: Use of Insufficiently Random Values) affecting Railties libraries in the RubyGems ecosystem. The issue involves use of insufficiently random values in railties allows remote code execution. Remediation is available by upgrading affected packages to version 5.2.2.1.

CVE-2019-5420 at a Glance

CVE Identifier CVE-2019-5420
GHSA Identifier GHSA-m42h-mh85-4qgc
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-330: Use of Insufficiently Random Values
Affected Product Railties
Package Ecosystem RubyGems
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:3.0/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-2019-5420

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

railties fixed: 5.2.2.1 
Upgrade railties to 5.2.2.1
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 railties

How to Check if You Are Affected

To determine whether your application is affected by CVE-2019-5420, inspect your project dependencies for Railties:

inspect dependencies for railties

Analyze the terminal output to locate any version of Railties in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.2.2.1), 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-330: Use of Insufficiently Random Values, where the product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers. In Railties, 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

# Possible Remote Code Execution Exploit in Rails Development Mode Impact ------ With some knowledge of a target application it is possible for an attacker to guess the automatically generated development mode secret token. This secret token can be used in combination with other Rails internals to escalate to a remote code execution exploit. All users running an affected release should either upgrade or use one of the workarounds immediately. Releases -------- The 6.0.0.beta3 and 5.2.2.1 releases are available at the normal locations. Workarounds ----------- This issue can be mitigated by specifying a secret key in development mode. In "config/environments/development.rb" add this: ``` config.secret_key_base = SecureRandom.hex(64) ``` Please note that only the 5.2.x, 5.1.x, 5.0.x, and 4.2.x series are supported at present. Users of earlier unsupported releases are advised to upgrade as soon as possible as we cannot guarantee the continued availability of security fixes for unsupported releases. Credits ------- Thanks to ooooooo_q

CVE-2019-5420 Affected Railties Versions

1 component(s)
Fixed Versions:
5.2.2.1
Product / Package Ecosystem Affected Versions Fixed Version
railties
gem/railties
RubyGems
≥ 5.2.0
< 5.2.2.1
5.2.2.1

References

NVD — CVE-2019-5420 NVD
https://nvd.nist.gov/vuln/detail/CVE-2019-5420
Railties Source Repository REPOSITORY
https://github.com/rubysec/ruby-advisory-db/blob/master/gems/railties/CVE-2019-5420.yml
groups.google.com/forum/ WEB
https://groups.google.com/forum/#!topic/rubyonrails-security/IsQKvDqZdKw
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/Y43636TH4D6T46IC6N2RQVJTRFJAAYGA
weblog.rubyonrails.org/2019/3/13/rails-4-2... WEB
https://weblog.rubyonrails.org/2019/3/13/Rails-4-2-5-1-5-1-6-2-have-been-released
www.exploit-db.com/exploits/46785 WEB
https://www.exploit-db.com/exploits/46785
Railties Security Information SECURITY
http://packetstormsecurity.com/files/152704/Ruby-On-Rails-DoubleTap-Development-Mode-secret_key_base-Remote-Code-Execution.html

Frequently Asked Questions

What is CVE-2019-5420?
CVE-2019-5420 is a security vulnerability in Railties involving Use of Insufficiently Random Values in Railties Allows Remote Code Execution under CWE-330: Use of Insufficiently Random Values.
Which Railties versions are affected?
Affected versions include releases prior to 5.2.2.1 across affected packages: railties.
What version fixes CVE-2019-5420?
Upgrading to 5.2.2.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is railties affected?
Yes, railties is affected in releases prior to 5.2.2.1. Upgrade your dependency to 5.2.2.1 or later.
What is the CVSS score of CVE-2019-5420?
CVE-2019-5420 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2019-5420?
CVE-2019-5420 is classified under CWE-330: Use of Insufficiently Random Values (The product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers.).
How can I check RubyGems dependencies for CVE-2019-5420?
Run the dependency tree command: 'inspect dependencies for railties'. 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-m42h-mh85-4qgc",
  "modified" : "2023-07-05T20:28:26Z",
  "published" : "2019-03-13T17:28:35Z",
  "aliases" : [ "CVE-2019-5420" ],
  "summary" : "Use of Insufficiently Random Values in Railties Allows Remote Code Execution",
  "details" : "# Possible Remote Code Execution Exploit in Rails Development Mode\n\nImpact \n------ \nWith some knowledge of a target application it is possible for an attacker to  guess the automatically generated development mode secret token.  This secret  token can be used in combination with other Rails internals to escalate to a remote code execution exploit. \n\nAll users running an affected release should either upgrade or use one of the workarounds immediately. \n\nReleases \n-------- \nThe 6.0.0.beta3 and 5.2.2.1 releases are available at the normal locations. \n\nWorkarounds \n----------- \nThis issue can be mitigated by specifying a secret key in development mode. \nIn \"config/environments/development.rb\" add this: \n\n```\n  config.secret_key_base = SecureRandom.hex(64) \n```\n\nPlease note that only the 5.2.x, 5.1.x, 5.0.x, and 4.2.x series are supported at present. Users of earlier unsupported releases are advised to upgrade as soon as possible as we cannot guarantee the continued availability of security fixes for unsupported releases. \n\nCredits \n------- \nThanks to ooooooo_q \n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "railties"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "5.2.0"
      }, {
        "fixed" : "5.2.2.1"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 5.2.2.0"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2019-5420"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/railties/CVE-2019-5420.yml"
  }, {
    "type" : "WEB",
    "url" : "https://groups.google.com/forum/#!topic/rubyonrails-security/IsQKvDqZdKw"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/Y43636TH4D6T46IC6N2RQVJTRFJAAYGA"
  }, {
    "type" : "WEB",
    "url" : "https://weblog.rubyonrails.org/2019/3/13/Rails-4-2-5-1-5-1-6-2-have-been-released"
  }, {
    "type" : "WEB",
    "url" : "https://www.exploit-db.com/exploits/46785"
  }, {
    "type" : "WEB",
    "url" : "http://packetstormsecurity.com/files/152704/Ruby-On-Rails-DoubleTap-Development-Mode-secret_key_base-Remote-Code-Execution.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-330", "CWE-77" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2020-06-16T21:44:46Z",
    "nvd_published_at" : "2019-03-27T14:29:00Z"
  }
}