GHSA-2XMW-F8J8-WFXC

Vulnerability from github – Published: 2026-07-28 22:25 – Updated: 2026-07-28 22:25
VLAI
Summary
Pagy I18n locale option is not validated before being used in a file path
Details

Summary

Pagy::I18n.locale= did not validate its argument before using it as a path component to load the matching dictionary file (<locale>.yml). An application that assigns untrusted input to the locale — e.g. the common pattern Pagy::I18n.locale = params[:locale] — let that input influence which file Pagy attempted to load.

Details

The setter stored the value as-is, and the loader joined it into a path and read it:

# gem/lib/pagy/modules/i18n/i18n.rb
def locale=(value)
  Thread.current[:pagy_locale] = value.to_s
end

# ...later, when translating:
path = pathnames.reverse.map { |p| p.join("#{locale}.yml") }.find(&:exist?)
dictionary = YAML.load_file(path)[locale]

Because the locale was used verbatim, a value such as an absolute path or a ../-style string redirected the lookup outside the locales directory. Pagy's subsequent structural check (dictionary['pagy']['p11n']) prevents the file's contents from being returned, so this is not a direct file read.

Fixed in 43.5.6 by constraining the locale to a BCP 47 shape before use:

LOCALE_PATTERN = /\A[a-zA-Z]{2,8}(-[a-zA-Z0-9]{1,8})*\z/

def locale=(value)
  Thread.current[:pagy_locale] = value.to_s[LOCALE_PATTERN]
end

Any non-matching value (including nil) resolves to the default locale and never reaches the file lookup.

PoC

In an application that sets Pagy::I18n.locale = params[:locale], the loader appends .yml and reads <locale>.yml, so the request param controls the target path. For example, pointing it at the app's config/database.yml:

  1. Send a request with ?locale=../../../config/database (adjust the number of ../ to reach the app root from the gem's locales/ directory).
  2. Pagy calls YAML.load_file on the resulting …/config/database.yml.
  3. The outcome differs by whether that .yml exists, is readable, parses as YAML, and has Pagy's expected structure — an existing, readable config/database.yml raises a different error than a non-existent path (which silently falls back to the default locale). This yields a file-existence / readability oracle for .yml paths, and the targeted file is read into the process during the attempt.

Impact

Information disclosure (CWE-22 / CWE-200): a file-existence / readability oracle for .yml paths on the host, plus a server-side read of attacker-chosen files into the process. The file contents are not returned in the response.

Only applications that pass unsanitized end-user input into Pagy::I18n.locale= are affected. Applications that set the locale from trusted values are not affected.

Patched: pagy 43.5.6. Workaround (if you cannot upgrade): validate the locale before assigning it, e.g. Pagy::I18n.locale = params[:locale].to_s[/\A[a-zA-Z]{2,8}(-[a-zA-Z0-9]{1,8})*\z/], or restrict it to your known set of locales.

Severity
6.9 (Medium)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Show details on source website
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{
  "affected": [
    {
      "package": {
        "ecosystem": "RubyGems",
        "name": "pagy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "43.0.0"
            },
            {
              "fixed": "43.5.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-54659"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-200",
      "CWE-22"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-28T22:25:29Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\n\n`Pagy::I18n.locale=` did not validate its argument before using it as a\npath component to load the matching dictionary file (`\u003clocale\u003e.yml`). An\napplication that assigns untrusted input to the locale \u2014 e.g. the common\npattern `Pagy::I18n.locale = params[:locale]` \u2014 let that input influence\nwhich file Pagy attempted to load.\n\n### Details\n\nThe setter stored the value as-is, and the loader joined it into a path\nand read it:\n\n```ruby\n# gem/lib/pagy/modules/i18n/i18n.rb\ndef locale=(value)\n  Thread.current[:pagy_locale] = value.to_s\nend\n\n# ...later, when translating:\npath = pathnames.reverse.map { |p| p.join(\"#{locale}.yml\") }.find(\u0026:exist?)\ndictionary = YAML.load_file(path)[locale]\n```\n\nBecause the locale was used verbatim, a value such as an absolute path or\na `../`-style string redirected the lookup outside the locales directory.\nPagy\u0027s subsequent structural check (`dictionary[\u0027pagy\u0027][\u0027p11n\u0027]`)\nprevents the file\u0027s contents from being returned, so this is **not** a\ndirect file read.\n\nFixed in 43.5.6 by constraining the locale to a BCP 47 shape before use:\n\n```ruby\nLOCALE_PATTERN = /\\A[a-zA-Z]{2,8}(-[a-zA-Z0-9]{1,8})*\\z/\n\ndef locale=(value)\n  Thread.current[:pagy_locale] = value.to_s[LOCALE_PATTERN]\nend\n```\n\nAny non-matching value (including `nil`) resolves to the default locale\nand never reaches the file lookup.\n\n### PoC\n\nIn an application that sets `Pagy::I18n.locale = params[:locale]`, the\nloader appends `.yml` and reads `\u003clocale\u003e.yml`, so the request param\ncontrols the target path. For example, pointing it at the app\u0027s\n`config/database.yml`:\n\n1. Send a request with `?locale=../../../config/database` (adjust the\n   number of `../` to reach the app root from the gem\u0027s `locales/`\n   directory).\n2. Pagy calls `YAML.load_file` on the resulting `\u2026/config/database.yml`.\n3. The outcome differs by whether that `.yml` exists, is readable, parses\n   as YAML, and has Pagy\u0027s expected structure \u2014 an existing, readable\n   `config/database.yml` raises a different error than a non-existent\n   path (which silently falls back to the default locale). This yields a\n   file-existence / readability oracle for `.yml` paths, and the targeted\n   file is read into the process during the attempt.\n\n### Impact\n\nInformation disclosure (CWE-22 / CWE-200): a file-existence / readability\noracle for `.yml` paths on the host, plus a server-side read of\nattacker-chosen files into the process. The file contents are not\nreturned in the response.\n\nOnly applications that pass **unsanitized end-user input** into\n`Pagy::I18n.locale=` are affected. Applications that set the locale from\ntrusted values are not affected.\n\n**Patched:** pagy 43.5.6.\n**Workaround (if you cannot upgrade):** validate the locale before\nassigning it, e.g.\n`Pagy::I18n.locale = params[:locale].to_s[/\\A[a-zA-Z]{2,8}(-[a-zA-Z0-9]{1,8})*\\z/]`,\nor restrict it to your known set of locales.",
  "id": "GHSA-2xmw-f8j8-wfxc",
  "modified": "2026-07-28T22:25:29Z",
  "published": "2026-07-28T22:25:29Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ddnexus/pagy/security/advisories/GHSA-2xmw-f8j8-wfxc"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ddnexus/pagy/pull/908"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ddnexus/pagy/commit/efcf09690e9fa7d7abdfb987b785a55f87e287df"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ddnexus/pagy"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ddnexus/pagy/releases/tag/43.5.6"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Pagy I18n locale option is not validated before being used in a file path"
}



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