CVE-2023-27539: Rack Denial of Service Vulnerability

LOW
Advisory Identifier: GHSA-c6qg-cjj8-47qp
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Published
Advisory Summary

CVE-2023-27539 is a LOW denial of service vulnerability (General Security Weakness) affecting Rack libraries in the RubyGems ecosystem. The issue involves possible denial of service vulnerability in rack's header parsing. Remediation is available by upgrading affected packages to version 2.2.6.4, 3.0.6.1.

CVE-2023-27539 at a Glance

CVE Identifier CVE-2023-27539
GHSA Identifier GHSA-c6qg-cjj8-47qp
Severity LOW
CVSS v3.1 Base Score N/A
CWE Classification General Security Weakness
Affected Product Rack
Package Ecosystem RubyGems
Published Date
Last Updated

How to Fix CVE-2023-27539

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: 2.2.6.4 
Upgrade rack to 2.2.6.4
rack fixed: 3.0.6.1 
Upgrade rack to 3.0.6.1
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 rack

How to Check if You Are Affected

To determine whether your application is affected by CVE-2023-27539, 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 2.2.6.4), 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 General Security Weakness. 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

There is a denial of service vulnerability in the header parsing component of Rack. This vulnerability has been assigned the CVE identifier CVE-2023-27539. Versions Affected: >= 2.0.0 Not affected: None. Fixed Versions: 2.2.6.4, 3.0.6.1 # Impact Carefully crafted input can cause header parsing in Rack to take an unexpected amount of time, possibly resulting in a denial of service attack vector. Any applications that parse headers using Rack (virtually all Rails applications) are impacted. # Workarounds Setting Regexp.timeout in Ruby 3.2 is a possible workaround.

CVE-2023-27539 Affected Rack Versions

2 component(s)
Fixed Versions:
2.2.6.43.0.6.1
Product / Package Ecosystem Affected Versions Fixed Version
rack
gem/rack
RubyGems
≥ 2.0.0
< 2.2.6.4
2.2.6.4
rack
gem/rack
RubyGems
≥ 3.0.0
< 3.0.6.1
3.0.6.1

References

Rack Source Repository REPOSITORY
https://github.com/rack/rack
NVD — CVE-2023-27539 NVD
https://nvd.nist.gov/vuln/detail/CVE-2023-27539
Security Fix Commit FIX COMMIT
https://github.com/rack/rack/commit/231ef369ad0b542575fb36c74fcfcfabcf6c530c
Security Fix Commit FIX COMMIT
https://github.com/rack/rack/commit/ee7919ea04303717858be1c3f16b406adc6d8cff
discuss.rubyonrails.org/t/cve-2023-27539-po... WEB
https://discuss.rubyonrails.org/t/cve-2023-27539-possible-denial-of-service-vulnerability-in-racks-header-parsing/82466
Rack Source Repository REPOSITORY
https://github.com/rubysec/ruby-advisory-db/blob/master/gems/rack/CVE-2023-27539.yml
lists.debian.org/debian-lts-announce... WEB
https://lists.debian.org/debian-lts-announce/2023/04/msg00017.html
Rack Security Information SECURITY
https://security.netapp.com/advisory/ntap-20231208-0016
Rack Security Information SECURITY
https://www.debian.org/security/2023/dsa-5530

Frequently Asked Questions

What is CVE-2023-27539?
CVE-2023-27539 is a security vulnerability in Rack involving Possible Denial of Service Vulnerability in Rack's header parsing under General Security Weakness.
Which Rack versions are affected?
Affected versions include releases prior to 2.2.6.4, 3.0.6.1 across affected packages: rack.
What version fixes CVE-2023-27539?
Upgrading to 2.2.6.4, 3.0.6.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is rack affected?
Yes, rack is affected in releases prior to 2.2.6.4, 3.0.6.1. Upgrade your dependency to 2.2.6.4, 3.0.6.1 or later.
What CWE is associated with CVE-2023-27539?
CVE-2023-27539 is classified under General Security Weakness.
How can I check RubyGems dependencies for CVE-2023-27539?
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-c6qg-cjj8-47qp",
  "modified" : "2025-01-09T15:36:58Z",
  "published" : "2023-03-15T21:36:02Z",
  "aliases" : [ "CVE-2023-27539" ],
  "summary" : "Possible Denial of Service Vulnerability in Rack's header parsing",
  "details" : "There is a denial of service vulnerability in the header parsing component of Rack. This vulnerability has been assigned the CVE identifier CVE-2023-27539.\n\nVersions Affected: >= 2.0.0 Not affected: None. Fixed Versions: 2.2.6.4, 3.0.6.1\n\n# Impact\nCarefully crafted input can cause header parsing in Rack to take an unexpected amount of time, possibly resulting in a denial of service attack vector. Any applications that parse headers using Rack (virtually all Rails applications) are impacted.\n\n# Workarounds\nSetting Regexp.timeout in Ruby 3.2 is a possible workaround.\n",
  "severity" : [ ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "rack"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.0.0"
      }, {
        "fixed" : "2.2.6.4"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "rack"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.0.0"
      }, {
        "fixed" : "3.0.6.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2023-27539"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rack/rack/commit/231ef369ad0b542575fb36c74fcfcfabcf6c530c"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rack/rack/commit/ee7919ea04303717858be1c3f16b406adc6d8cff"
  }, {
    "type" : "WEB",
    "url" : "https://discuss.rubyonrails.org/t/cve-2023-27539-possible-denial-of-service-vulnerability-in-racks-header-parsing/82466"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/rack/rack"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/rack/CVE-2023-27539.yml"
  }, {
    "type" : "WEB",
    "url" : "https://lists.debian.org/debian-lts-announce/2023/04/msg00017.html"
  }, {
    "type" : "WEB",
    "url" : "https://security.netapp.com/advisory/ntap-20231208-0016"
  }, {
    "type" : "WEB",
    "url" : "https://www.debian.org/security/2023/dsa-5530"
  } ],
  "database_specific" : {
    "cwe_ids" : [ ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2023-03-15T21:36:02Z",
    "nvd_published_at" : "2025-01-09T01:15:07Z"
  }
}