CVE-2020-8184: Rack Remote Code Execution Vulnerability

HIGH
Advisory Identifier: GHSA-j6w9-fv6q-3q52
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CVSS 7.5
CWE-20 CWE-784
Published
Advisory Summary

CVE-2020-8184 is a HIGH (CVSS 7.5) remote code execution vulnerability (CWE-20: Improper Input Validation) affecting Rack libraries in the RubyGems ecosystem. The issue involves rack allows percent-encoded cookies to overwrite existing prefixed cookie names. Remediation is available by upgrading affected packages to version 2.1.4, 2.2.3.

CVE-2020-8184 at a Glance

CVE Identifier CVE-2020-8184
GHSA Identifier GHSA-j6w9-fv6q-3q52
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-20: Improper Input Validation
Affected Product Rack
Package Ecosystem RubyGems
Published Date
Last Updated

Security Impact

CVSS: 7.5

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:N/I:H/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 None (C:N)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2020-8184

To remediate this vulnerability, upgrade all affected Rack 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 fixed: 2.1.4 
Upgrade rack to 2.1.4
rack fixed: 2.2.3 
Upgrade rack to 2.2.3
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

How to Check if You Are Affected

To determine whether your application is affected by CVE-2020-8184, inspect your project dependencies for Rack:

inspect dependencies for rack

Analyze the terminal output to locate any version of Rack in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.1.4), 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-20: Improper Input Validation, where the product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. In Rack, 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 reliance on cookies without validation/integrity check security vulnerability exists in rack < 2.2.3, rack < 2.1.4 that makes it possible for an attacker to forge a secure or host-only cookie prefix.

CVE-2020-8184 Affected Rack Versions

2 component(s)
Fixed Versions:
2.1.42.2.3
Product / Package Ecosystem Affected Versions Fixed Version
rack
gem/rack
RubyGems
< 2.1.4
2.1.4
rack
gem/rack
RubyGems
≥ 2.2.0
< 2.2.3
2.2.3

References

NVD — CVE-2020-8184 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-8184
Security Fix Commit FIX COMMIT
https://github.com/rack/rack/commit/1f5763de6a9fe515ff84992b343d63c88104654c
hackerone.com/reports/895727 WEB
https://hackerone.com/reports/895727
Rack Source Repository REPOSITORY
https://github.com/rack/rack
Rack Source Repository REPOSITORY
https://github.com/rubysec/ruby-advisory-db/blob/master/gems/rack/CVE-2020-8184.yml
Rack Security Information SECURITY
https://groups.google.com/g/rubyonrails-security/c/OWtmozPH9Ak
lists.debian.org/debian-lts-announce... WEB
https://lists.debian.org/debian-lts-announce/2020/07/msg00006.html
lists.debian.org/debian-lts-announce... WEB
https://lists.debian.org/debian-lts-announce/2023/01/msg00038.html
usn.ubuntu.com/4561-1 WEB
https://usn.ubuntu.com/4561-1

Frequently Asked Questions

What is CVE-2020-8184?
CVE-2020-8184 is a security vulnerability in Rack involving Rack allows Percent-encoded cookies to overwrite existing prefixed cookie names under CWE-20: Improper Input Validation.
Which Rack versions are affected?
Affected versions include releases prior to 2.1.4, 2.2.3 across affected packages: rack.
What version fixes CVE-2020-8184?
Upgrading to 2.1.4, 2.2.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is rack affected?
Yes, rack is affected in releases prior to 2.1.4, 2.2.3. Upgrade your dependency to 2.1.4, 2.2.3 or later.
What is the CVSS score of CVE-2020-8184?
CVE-2020-8184 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
What CWE is associated with CVE-2020-8184?
CVE-2020-8184 is classified under CWE-20: Improper Input Validation (The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.).
How can I check RubyGems dependencies for CVE-2020-8184?
Run the dependency tree command: 'inspect dependencies for rack'. 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-j6w9-fv6q-3q52",
  "modified" : "2023-08-28T12:13:59Z",
  "published" : "2020-06-24T17:15:00Z",
  "aliases" : [ "CVE-2020-8184" ],
  "summary" : "Rack allows Percent-encoded cookies to overwrite existing prefixed cookie names",
  "details" : "A reliance on cookies without validation/integrity check security vulnerability exists in rack < 2.2.3, rack < 2.1.4 that makes it possible for an attacker to forge a secure or host-only cookie prefix.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "rack"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.1.4"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "rack"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.2.0"
      }, {
        "fixed" : "2.2.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-8184"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rack/rack/commit/1f5763de6a9fe515ff84992b343d63c88104654c"
  }, {
    "type" : "WEB",
    "url" : "https://hackerone.com/reports/895727"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/rack/rack"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/rack/CVE-2020-8184.yml"
  }, {
    "type" : "WEB",
    "url" : "https://groups.google.com/g/rubyonrails-security/c/OWtmozPH9Ak"
  }, {
    "type" : "WEB",
    "url" : "https://lists.debian.org/debian-lts-announce/2020/07/msg00006.html"
  }, {
    "type" : "WEB",
    "url" : "https://lists.debian.org/debian-lts-announce/2023/01/msg00038.html"
  }, {
    "type" : "WEB",
    "url" : "https://usn.ubuntu.com/4561-1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20", "CWE-784" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2020-06-24T17:14:36Z",
    "nvd_published_at" : "2020-06-19T17:15:00Z"
  }
}