We have released the StringIO gem version 3.0.1.1 and 3.0.1.2 that have a security fix for a buffer overread vulnerability.
This vulnerability has been assigned the CVE identifier [CVE-2024-27280](https://www.cve.org/CVERecord?id=CVE-2024-27280).

## Details

An issue was discovered in StringIO 3.0.1, as distributed in Ruby 3.0.x through 3.0.6 and 3.1.x through 3.1.4.

The `ungetbyte` and `ungetc` methods on a StringIO can read past the end of a string, and a subsequent call to `StringIO.gets` may return the memory value.

This vulnerability is not affected StringIO 3.0.3 and later, and Ruby 3.2.x and later.

## Recommended action

We recommend to update the StringIO gem to version 3.0.3 or later. In order to ensure compatibility with bundled version in older Ruby series, you may update as follows instead:

* For Ruby 3.0 users: Update to `stringio` 3.0.1.1
* For Ruby 3.1 users: Update to `stringio` 3.0.1.2

Note: that StringIO 3.0.1.2 contains not only the fix for this vulnerability but also a bugfix for [[Bug #19389]](https://github.com/ruby/ruby/commit/1d24a931c458c93463da1d5885f33edef3677cc2).

You can use `gem update stringio` to update it. If you are using bundler, please add `gem "stringio", ">= 3.0.1.2"` to your `Gemfile`.

## Affected versions

* Ruby 3.0.6 or lower
* Ruby 3.1.4 or lower
* StringIO gem 3.0.1 or lower

## Credits

Thanks to [david_h1](https://hackerone.com/david_h1?type=user) for discovering this issue.

## History

* Fixed the affected version of StringIO (3.0.2 -> 3.0.1) at 2024-04-11 12:50:00 (UTC)
* Originally published at 2024-03-21 4:00:00 (UTC)