CVE-2019-18978: Rack cors The Rack-cors Rubygem May Allow Vulnerability

MODERATE
Advisory Identifier: GHSA-pf8f-w267-mq2h
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CVSS 5.3
CWE-22
Published
Advisory Summary

CVE-2019-18978 is a MODERATE (CVSS 5.3) the rack-cors rubygem may allow vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Rack cors libraries in the RubyGems ecosystem. The issue involves the rack-cors rubygem may allow directory traveral. Remediation is available by upgrading affected packages to version 1.0.4.

CVE-2019-18978 at a Glance

CVE Identifier CVE-2019-18978
GHSA Identifier GHSA-pf8f-w267-mq2h
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Affected Product Rack cors
Package Ecosystem RubyGems
Published Date
Last Updated

Security Impact

CVSS: 5.3

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:L/I:N/A:N).

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 Low (C:L)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2019-18978

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

rack-cors fixed: 1.0.4 
Upgrade rack-cors to 1.0.4
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 rack-cors

How to Check if You Are Affected

To determine whether your application is affected by CVE-2019-18978, inspect your project dependencies for Rack cors:

inspect dependencies for rack-cors

Analyze the terminal output to locate any version of Rack cors in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.0.4), 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-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), where the product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. In Rack cors, 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 the rack-cors (aka Rack CORS Middleware) gem before 1.0.4 for Ruby. It allows ../ directory traversal to access private resources because resource matching does not ensure that pathnames are in a canonical format.

CVE-2019-18978 Affected Rack cors Versions

1 component(s)
Fixed Versions:
1.0.4
Product / Package Ecosystem Affected Versions Fixed Version
rack-cors
gem/rack-cors
RubyGems
< 1.0.4
1.0.4

References

NVD — CVE-2019-18978 NVD
https://nvd.nist.gov/vuln/detail/CVE-2019-18978
Security Fix Commit FIX COMMIT
https://github.com/cyu/rack-cors/commit/e4d4fc362a4315808927011cbe5afcfe5486f17d
Rack cors Source Repository REPOSITORY
https://github.com/cyu/rack-cors
Rack cors Source Repository REPOSITORY
https://github.com/cyu/rack-cors/compare/v1.0.3...v1.0.4
lists.debian.org/debian-lts-announce... WEB
https://lists.debian.org/debian-lts-announce/2020/02/msg00004.html
lists.debian.org/debian-lts-announce... WEB
https://lists.debian.org/debian-lts-announce/2020/10/msg00000.html
usn.ubuntu.com/4571-1 WEB
https://usn.ubuntu.com/4571-1
Rack cors Security Information SECURITY
https://www.debian.org/security/2021/dsa-4918

Frequently Asked Questions

What is CVE-2019-18978?
CVE-2019-18978 is a security vulnerability in Rack cors involving The rack-cors rubygem may allow directory traveral under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').
Which Rack cors versions are affected?
Affected versions include releases prior to 1.0.4 across affected packages: rack-cors.
What version fixes CVE-2019-18978?
Upgrading to 1.0.4 (or the latest patched release for your respective branch) resolves the vulnerability.
Is rack-cors affected?
Yes, rack-cors is affected in releases prior to 1.0.4. Upgrade your dependency to 1.0.4 or later.
What is the CVSS score of CVE-2019-18978?
CVE-2019-18978 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.
What CWE is associated with CVE-2019-18978?
CVE-2019-18978 is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.).
How can I check RubyGems dependencies for CVE-2019-18978?
Run the dependency tree command: 'inspect dependencies for rack-cors'. 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-pf8f-w267-mq2h",
  "modified" : "2023-01-23T20:22:08Z",
  "published" : "2019-11-15T20:26:59Z",
  "aliases" : [ "CVE-2019-18978" ],
  "summary" : "The rack-cors rubygem may allow directory traveral",
  "details" : "An issue was discovered in the rack-cors (aka Rack CORS Middleware) gem before 1.0.4 for Ruby. It allows ../ directory traversal to access private resources because resource matching does not ensure that pathnames are in a canonical format.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "rack-cors"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.0.4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2019-18978"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/cyu/rack-cors/commit/e4d4fc362a4315808927011cbe5afcfe5486f17d"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/cyu/rack-cors"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/cyu/rack-cors/compare/v1.0.3...v1.0.4"
  }, {
    "type" : "WEB",
    "url" : "https://lists.debian.org/debian-lts-announce/2020/02/msg00004.html"
  }, {
    "type" : "WEB",
    "url" : "https://lists.debian.org/debian-lts-announce/2020/10/msg00000.html"
  }, {
    "type" : "WEB",
    "url" : "https://usn.ubuntu.com/4571-1"
  }, {
    "type" : "WEB",
    "url" : "https://www.debian.org/security/2021/dsa-4918"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2019-11-15T20:26:35Z",
    "nvd_published_at" : "2019-11-14T21:15:00Z"
  }
}