🚨 [security] [ruby] Update rails 8.1.3 → 8.1.3.1 (minor)

[depfu]

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🚨 Your current dependencies have known security vulnerabilities 🚨

This dependency update fixes known security vulnerabilities. Please see the details below and assess their impact carefully. We recommend to merge and deploy this as soon as possible!

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Here is everything you need to know about this update. Please take a good look at what changed and the test results before merging this pull request.

What changed?

✳️ rails (8.1.3 → 8.1.3.1) · Repo · Changelog

Release Notes

8.1.3.1

Active Support

• No changes.

Active Model

• No changes.

Active Record

• No changes.

Action View

• No changes.

Action Pack

• No changes.

Active Job

• No changes.

Action Mailer

• No changes.

Action Cable

• No changes.

Active Storage

• Disable libvips's unfuzzed image loaders and savers.

  libvips flags some of its loaders and savers as "unfuzzed" or "untrusted", meaning they are only
  safe for trusted content. Active Storage will call Vips.block_untrusted(true) to disable them
  while booting. An application that needs a specific loader or saver may re-enable it in an
  initializer.

  This is a breaking change for applications that process image types with an unfuzzed loader or
  saver. Variant transformation of BMP, ICO, and PSD attachments will raise Vips::Error, and
  analysis of these and other types such as SVG, JPEG XL, JPEG 2000, and Netpbm will no longer
  record width and height. Requesting an unfuzzed output format, typically FITS, JXL, or
  anything delegated to ImageMagick, will also raise Vips::Error. Attaching, storing, and
  downloading are unchanged.

  An application seeing Vips::Error raised during image transformation may wish to remove the
  affected content types from config.active_storage.variable_content_types in an initializer.
  Active Storage will then treat those attachments as not variable and will not generate variants
  for them. This most often matters to an application that transforms images during a request
  rather than in a background job, where the failure surfaces as an error response instead of a
  failed job.

  Rails.application.config.active_storage.variable_content_types -=
    %w[ image/bmp image/vnd.microsoft.icon image/vnd.adobe.photoshop ]

  Applications using the :mini_magick variant processor will see no change in how their
  attachments are processed, but the loaders and savers will be disabled process-wide whenever
  ruby-vips is installed, and the version requirements below will still apply. Such an application
  may remove ruby-vips from its Gemfile to avoid both.

  The minimum supported version of libvips is now 8.13, and the minimum supported version of
  ruby-vips is now 2.2.1. These are the earliest versions that are capable of disabling untrusted
  operations. When ruby-vips is installed and either minimum is not met, Active Storage will raise
  a RuntimeError while booting rather than run in an unsecurable environment.

  [GHSA-xr9x-r78c-5hrm]
  [CVE-2026-66066]

  Mike Dalessio

Action Mailbox

• No changes.

Action Text

• No changes.

Railties

• No changes.

Guides

• No changes.

Does any of this look wrong? Please let us know.

Commits

See the full diff on Github. The new version differs by 1 commit:

• Preparing for 8.1.3.1 release

↗️ actioncable (indirect, 8.1.3 → 8.1.3.1) · Repo · Changelog

Commits

See the full diff on Github. The new version differs by 1 commit:

• Preparing for 8.1.3.1 release

↗️ actionmailbox (indirect, 8.1.3 → 8.1.3.1) · Repo · Changelog

Commits

See the full diff on Github. The new version differs by 1 commit:

• Preparing for 8.1.3.1 release

↗️ actionmailer (indirect, 8.1.3 → 8.1.3.1) · Repo · Changelog

Commits

See the full diff on Github. The new version differs by 1 commit:

• Preparing for 8.1.3.1 release

↗️ actionpack (indirect, 8.1.3 → 8.1.3.1) · Repo · Changelog

Commits

See the full diff on Github. The new version differs by 1 commit:

• Preparing for 8.1.3.1 release

↗️ actiontext (indirect, 8.1.3 → 8.1.3.1) · Repo · Changelog

Commits

See the full diff on Github. The new version differs by 1 commit:

• Preparing for 8.1.3.1 release

↗️ actionview (indirect, 8.1.3 → 8.1.3.1) · Repo · Changelog

Commits

See the full diff on Github. The new version differs by 1 commit:

• Preparing for 8.1.3.1 release

↗️ activejob (indirect, 8.1.3 → 8.1.3.1) · Repo · Changelog

Commits

See the full diff on Github. The new version differs by 1 commit:

• Preparing for 8.1.3.1 release

↗️ activemodel (indirect, 8.1.3 → 8.1.3.1) · Repo · Changelog

Commits

See the full diff on Github. The new version differs by 1 commit:

• Preparing for 8.1.3.1 release

↗️ activerecord (indirect, 8.1.3 → 8.1.3.1) · Repo · Changelog

Commits

See the full diff on Github. The new version differs by 1 commit:

• Preparing for 8.1.3.1 release

↗️ activestorage (indirect, 8.1.3 → 8.1.3.1) · Repo · Changelog

Security Advisories 🚨

🚨 Active Storage has possible arbitrary file read and remote code execution in Active Storage variant processing

Impact

In its default configuration, a Rails application that displays image variants may allow an
unauthenticated attacker to read arbitrary files from the server, including the process environment.
That environment typically holds secret_key_base and often credentials for external systems, which
may in turn allow escalation to remote code execution or lateral movement to those systems.

Details

libvips reads and writes file formats through "loaders" and "savers" (or more generally
"operations"), many of which are backed by third-party libraries. It marks some of these operations
as "unfuzzed", meaning they are unsafe for untrusted content, and several handle formats unrelated
to web images. Active Storage did not disable the unfuzzed operations, so an attacker who can upload
a crafted file and cause a variant to be generated from it may be able to invoke one.

We are aware of a mechanism by which an attacker, by uploading a crafted file, is able to cause
disclosure of the contents of arbitrary files accessible on the filesystem of the targeted
application. One specific attack chain has been reported to us (see "Disclosure" below), but we do
not assume it is the only one that exists.

Affected applications

An application is affected if it meets all of these requirements:

• Uses libvips for Active Storage image processing. This is config.active_storage.variant_processor = :vips,
  which load_defaults 7.0 set and no later default has changed.
• Allows image uploads from untrusted users.

Generating variants is not a separate requirement.

Mitigation

• Upgrade to a fixed version of activestorage.
• The minimum version of libvips must be upgraded to >= 8.13.
• Change secret_key_base and change any secrets accessible in the application environment (see "Expire and change secrets" below)

Earlier versions of libvips (< 8.13) cannot disable unfuzzed operations at all, and Active Storage
will raise an exception during boot in such an unsecurable environment.

Expire and change secrets

Upgrading closes the vulnerability but does not undo an exfiltrated secret if that already
occurred. An affected application should treat every secret readable by the application process as
potentially exposed and change it, including:

• secret_key_base
• The master key, whether stored in config/master.key or supplied as RAILS_MASTER_KEY, along
  with everything in config/credentials.yml.enc that it decrypts
• Credentials for the Active Storage service, such as S3, GCS, or Azure keys
• Database credentials
• Tokens and keys for any third-party service the application calls

Changing secret_key_base expires active sessions and requires users to log in again. Encrypted
cookies, signed cookies, signed global IDs, and Active Storage URLs are also affected.

Rotation should only be used as an intermediate step if necessary. Do not retain an exposed secret
as a fallback.

Workarounds

If libvips < 8.13 is being used, there are no workarounds available other than removing the
dependency on libvips from the application. Some applications may have ruby-vips declared as a
dependency only for image analysis, and those applications may be able to simply remove ruby-vips
from the Gemfile to remove libvips from the application. Applications that do not use Active Storage
can remove ruby-vips from the Gemfile to avoid the boot-time checks.

If libvips >= 8.13 is present on the system, applications can disable the unfuzzed operations
without upgrading Rails by setting the VIPS_BLOCK_UNTRUSTED environment variable, which libvips
reads while initializing.

Applications also running ruby-vips >= 2.2.1 or later can instead call
Vips.block_untrusted(true) from an initializer.

Releases

The fixed releases are available at the normal locations.

Versions affected

• activestorage < 7.2.3.2
• activestorage >= 8.0, < 8.0.5.1
• activestorage >= 8.1, < 8.1.3.1

Disclosure

Technical details of the attack chain are intentionally omitted from this advisory. They would add
nothing to an administrator's decision to upgrade, while making it substantially easier to attack
applications that have not yet done so.

Details will be disclosed no later than 2026-08-28, via the Rails Security
Announcements forum.

Credit

This issue was responsibly reported by 0xacb, s3np41k1r1t0 and castilho from Ethiack, and RyotaK from GMO Flatt Security Inc..

References

• libvips 8.13 release notes, blocking of unfuzzed loaders
• W.A. Arbaugh, W.L. Fithen, and J. McHugh, "Windows of Vulnerability: A Case Study
  Analysis", IEEE Computer 33(12), December 2000
• https://ethiack.com/info-hub/research/kindarails2shell-rails-rce-cve
• https://blog.flatt.tech/entry/kindarails2shell_rails

Commits

See the full diff on Github. The new version differs by 1 commit:

• Preparing for 8.1.3.1 release

↗️ activesupport (indirect, 8.1.3 → 8.1.3.1) · Repo · Changelog

Commits

See the full diff on Github. The new version differs by 1 commit:

• Preparing for 8.1.3.1 release

↗️ railties (indirect, 8.1.3 → 8.1.3.1) · Repo · Changelog

Commits

See the full diff on Github. The new version differs by 1 commit:

• Preparing for 8.1.3.1 release

↗️ rbs (indirect, 4.1.0 → 4.1.1) · Repo · Changelog

Commits

See the full diff on Github. The new version differs by 23 commits:

• Merge pull request #3052 from ruby/release-4.1.1
• Version 4.1.1
• Merge pull request #3051 from ruby/release-4.1.1.pre.1
• Version 4.1.1.pre.1
• Merge pull request #3049 from ruby/claude/release-automation-4-1-1-dev-1-q846xm
• Version 4.1.1.dev.1
• Merge pull request #3047 from ruby/build-gems-workflow
• Release the gems from a workflow
• Merge pull request #3048 from ruby/changelog-base-by-version
• Pick the changelog base from the version being released
• Merge pull request #3046 from ruby/remove-milestone-check
• Remove the milestone check
• Merge pull request #3045 from ruby/gem-changelog-task
• Document preparing the release and starting the next cycle
• Generate the changelog from the previous release tag
• Merge pull request #3043 from ruby/keyword-key-question-location
• Include the trailing `?` in a keyword key's symbol location
• Merge pull request #3039 from ruby/alias-annotation-optional-type-name
• Mark `type_name` as optional on the alias annotations
• Merge pull request #3038 from ruby/fix-template-ci
• Version 4.1.1.pre
• Derive `confirm_templates` targets from the template list
• Apply `namespace` parameter rename to the template

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