CVE-2023-28846: Unpoly rails Denial of Service Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-m875-3xf6-mf78",
  "modified" : "2023-04-07T22:54:15Z",
  "published" : "2023-03-30T22:58:38Z",
  "aliases" : [ "CVE-2023-28846" ],
  "summary" : "unpoly-rails Denial of Service vulnerability",
  "details" : "There is a possible Denial of Service (DoS) vulnerability in the unpoly-rails gem that implements the [Unpoly server protocol](https://unpoly.com/up.protocol) for Rails applications.\n\n### Impact\n\nThis issues affects Rails applications that operate as an upstream of a load balancer's that uses [passive health checks](https://docs.nginx.com/nginx/admin-guide/load-balancer/http-health-check/#passive-health-checks).\n\nThe [unpoly-rails](https://github.com/unpoly/unpoly-rails/) gem echoes the request URL as an `X-Up-Location` response header. By making a request with exceedingly long URLs (paths or query string), an attacker can cause unpoly-rails to write a exceedingly large response header.\n\nIf the response header is too large to be parsed by a load balancer downstream of the Rails application, it may cause the load balancer to remove the upstream from a load balancing group. This causes that application instance to become unavailable until a configured timeout is reached or until an active healthcheck succeeds.\n\n\n### Patches\n\nThe fixed release 2.7.2.2+ is available via RubyGems and GitHub.\n\n\n### Workarounds\n\nIf you cannot upgrade to a fixed release, several workarounds are available:\n\n- Configure your load balancer to use active health checks, e.g. by periodically requesting a route with a known response that indicates healthiness.\n- Configure your load balancer so the [maximum size of response headers](https://makandracards.com/operations/537537-nginx-proxy-buffer-tuning) is at least twice the [maximum size of a URL](https://tryhexadecimal.com/guides/http/414-request-uri-too-long).\n- Instead of changing your server configuration you may also configure your Rails application to delete redundant `X-Up-Location` headers set by unpoly-rails:\n  \n  ```ruby\n  class ApplicationController < ActionController::Base\n  \n    after_action :remove_redundant_up_location_header\n    \n    private\n    \n    def remove_redundant_up_location_header\n      if request.original_url == response.headers['X-Up-Location']\n        response.headers.delete('X-Up-Location')\n      end\n    end\n  \n  end\n  ```",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "unpoly-rails"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.7.2.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/unpoly/unpoly-rails/security/advisories/GHSA-m875-3xf6-mf78"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2023-28846"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/unpoly/unpoly-rails/commit/cd9ad0007daceeb3b2354fdcab4f88350427bf16"
  }, {
    "type" : "WEB",
    "url" : "https://docs.nginx.com/nginx/admin-guide/load-balancer/http-health-check/#passive-health-checks"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/unpoly-rails/CVE-2023-28846.yml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/unpoly/unpoly-rails"
  }, {
    "type" : "WEB",
    "url" : "https://makandracards.com/operations/537537-nginx-proxy-buffer-tuning"
  }, {
    "type" : "WEB",
    "url" : "https://tryhexadecimal.com/guides/http/414-request-uri-too-long"
  }, {
    "type" : "WEB",
    "url" : "https://unpoly.com/up.protocol"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2023-03-30T22:58:38Z",
    "nvd_published_at" : "2023-03-30T20:15:00Z"
  }
}