Rails Active Support has a possible DoS vulnerability in its number helpers

Impact

Active Support number helpers accept strings containing scientific notation (e.g. 1e10000), which when converted to a string could be expanded into extremely large decimal representations. This can cause excessive memory allocation and CPU consumption when the expanded number is formatted, possibly resulting in a DoS vulnerability.

Releases

The fixed releases are available at the normal locations.

Credit

This issue was responsibly reported by Hackerone researcher manun.

Rails Active Support has a possible XSS vulnerability in SafeBuffer#%

Impact

SafeBuffer#% does not propagate the @html_unsafe flag to the newly created buffer. If a SafeBuffer is mutated in place (e.g. via gsub!) and then formatted with % using untrusted arguments, the result incorrectly reports html_safe? == true, bypassing ERB auto-escaping and possibly leading to XSS.

Releases

The fixed releases are available at the normal locations.

Credit

This issue was responsibly reported by @ch4n3-yoon

Rails Active Support has a possible ReDoS vulnerability in number_to_delimited

Impact

NumberToDelimitedConverter used a regular expression with gsub! to insert thousands delimiters. This could produce quadratic time complexity on long digit strings.

Releases

The fixed releases are available at the normal locations.

Credit

This issue was responsibly reported by Hackerone researcher scyoon.

Active Support Possibly Discloses Locally Encrypted Files

There is a possible file disclosure of locally encrypted files in Active Support. This vulnerability has been assigned the CVE identifier CVE-2023-38037.

Versions Affected: >= 5.2.0 Not affected: < 5.2.0 Fixed Versions: 7.0.7.1, 6.1.7.5

Impact

ActiveSupport::EncryptedFile writes contents that will be encrypted to a temporary file. The temporary file’s permissions are defaulted to the user’s current umask settings, meaning that it’s possible for other users on the same system to read the contents of the temporary file.

Attackers that have access to the file system could possibly read the contents of this temporary file while a user is editing it.

All users running an affected release should either upgrade or use one of the workarounds immediately.

Releases

The fixed releases are available at the normal locations.

Workarounds

To work around this issue, you can set your umask to be more restrictive like this:

$ umask 0077

Possible XSS Security Vulnerability in SafeBuffer#bytesplice

There is a vulnerability in ActiveSupport if the new bytesplice method is called on a SafeBuffer with untrusted user input. This vulnerability has been assigned the CVE identifier CVE-2023-28120.

Versions Affected: All. Not affected: None Fixed Versions: 7.0.4.3, 6.1.7.3

Impact

ActiveSupport uses the SafeBuffer string subclass to tag strings as htmlsafe after they have been sanitized. When these strings are mutated, the tag is should be removed to mark them as no longer being htmlsafe.

Ruby 3.2 introduced a new bytesplice method which ActiveSupport did not yet understand to be a mutation. Users on older versions of Ruby are likely unaffected.

All users running an affected release and using bytesplice should either upgrade or use one of the workarounds immediately.

Workarounds

Avoid calling bytesplice on a SafeBuffer (html_safe) string with untrusted user input.

Possible XSS Security Vulnerability in SafeBuffer#bytesplice

There is a vulnerability in ActiveSupport if the new bytesplice method is called on a SafeBuffer with untrusted user input. This vulnerability has been assigned the CVE identifier CVE-2023-28120.

Versions Affected: All. Not affected: None Fixed Versions: 7.0.4.3, 6.1.7.3

Impact

ActiveSupport uses the SafeBuffer string subclass to tag strings as htmlsafe after they have been sanitized. When these strings are mutated, the tag is should be removed to mark them as no longer being htmlsafe.

Ruby 3.2 introduced a new bytesplice method which ActiveSupport did not yet understand to be a mutation. Users on older versions of Ruby are likely unaffected.

All users running an affected release and using bytesplice should either upgrade or use one of the workarounds immediately.

Workarounds

Avoid calling bytesplice on a SafeBuffer (html_safe) string with untrusted user input.

Possible File Disclosure of Locally Encrypted Files

There is a possible file disclosure of locally encrypted files in Active Support. This vulnerability has been assigned the CVE identifier CVE-2023-38037.

• Versions Affected: >= 5.2.0
• Not affected: < 5.2.0
• Fixed Versions: 7.0.7.1, 6.1.7.5

Impact

ActiveSupport::EncryptedFile writes contents that will be encrypted to a temporary file. The temporary file’s permissions are defaulted to the user’s current umask settings, meaning that it’s possible for other users on the same system to read the contents of the temporary file.

Attackers that have access to the file system could possibly read the contents of this temporary file while a user is editing it.

All users running an affected release should either upgrade or use one of the workarounds immediately.

Releases

The fixed releases are available at the normal locations.

Workarounds

To work around this issue, you can set your umask to be more restrictive like this:

$ umask 0077

Rails Active Support has a possible ReDoS vulnerability in number_to_delimited

Impact

NumberToDelimitedConverter used a regular expression with gsub! to insert thousands delimiters. This could produce quadratic time complexity on long digit strings.

Releases

The fixed releases are available at the normal locations.

Rails Active Support has a possible XSS vulnerability in SafeBuffer#%

Impact

SafeBuffer#% does not propagate the @html_unsafe flag to the newly created buffer. If a SafeBuffer is mutated in place (e.g. via gsub!) and then formatted with % using untrusted arguments, the result incorrectly reports html_safe? == true, bypassing ERB auto-escaping and possibly leading to XSS.

Releases

The fixed releases are available at the normal locations.

Rails Active Support has a possible DoS vulnerability in its number helpers

Impact

Active Support number helpers accept strings containing scientific notation (e.g. 1e10000), which when converted to a string could be expanded into extremely large decimal representations. This can cause excessive memory allocation and CPU consumption when the expanded number is formatted, possibly resulting in a DoS vulnerability.

Releases

The fixed releases are available at the normal locations.

Possible DoS vulnerability in Active Support safe_constantize

Impact

When constant lookup raises LoadError, ActiveSupport::Inflector#safe_constantize (and String#safe_constantize) builds a regular expression from the requested constant name without escaping it, so a caller that passes untrusted input lets the attacker choose the source of a pattern that the application compiles. Crafted patterns can trigger defects in Ruby's regular expression compiler, possibly leading to a crash of the server process, and repeated requests could keep the application unavailable.

Action Cable passes the channel value of each subscribe command to safe_constantize before any channel lookup, so in the default configuration an unauthenticated client of the Action Cable endpoint can reach this code.

Details

The check that decides whether safe_constantize returns nil or re-raises the LoadError now matches the first segment of the constant name against the error message as a literal string, and no longer compiles a regular expression. It returns the same result as before for constant names that contain no regular expression syntax.

Affected applications

An application is affected if it meets all of these requirements: - Mounts Action Cable, which a new Rails application does by default at /cable (config.action_cable.mount_path), or otherwise passes untrusted input to safe_constantize. - Accepts Action Cable connections from untrusted clients. ApplicationCable::Connection#connect authenticates nobody unless the application adds a check.

Workarounds

Applications that do not use Action Cable can set config.action_cable.mount_path = nil to remove the endpoint. Applications that use Action Cable can call reject_unauthorized_connection in ApplicationCable::Connection#connect for unauthenticated clients, which limits exposure to authenticated users but does not remove it.

Releases

The fixed releases are available at the normal locations.

Patches for those who cannot upgrade at once: - 8.1: https://github.com/rails/rails/commit/95aa9e416016524956d4904fed96eaed079580bb.patch - 8.0: https://github.com/rails/rails/commit/210ac22d446c8e2625b091e79256806b836eee20.patch

Versions affected

• activesupport < 8.0.5.2
• activesupport >= 8.1, < 8.1.4.1

Credit

This issue was responsibly reported by Felix Tscheulin (flixt) through HackerOne researcher scheja, and independently by Bucky Wolfe (Igneous), who provided a proof of concept that crashes the server. It was also found by the Anthropic OSS Scanner (ANT-2026-ZUN5KU3Q).