Impact

The MessagesController class of OpenProject has a quote method that implements the logic behind the Quote button in the discussion forums, and it uses the following regex to strip <pre> tags from the message being quoted (app/controllers/messages_controller.rb#L147):

text.to_s.strip.gsub(%r{<pre>((.|\s)*?)</pre>}m, '[...]')

The (.|\s) part can match a space character in two ways, so an unterminated <pre> tag containing n spaces causes Ruby's regex engine to backtrack to try 2ⁿ states in the NFA. This will result in a Regular Expression Denial of Service.

Patches

The vulnerability has been introduced in Redmine before forking it. It is present in all OpenProject versions up to, and including, version 11.3.2. The issue is fixed in OpenProject 11.3.3

Workarounds

The vulnerability can also be fixed by applying the following patch: https://github.com/opf/openproject/pull/9447.patch

References

• https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS
• https://cwe.mitre.org/data/definitions/1333.html
• https://www.regular-expressions.info/catastrophic.html

For more information

If you have any questions or comments about this advisory:

• Open an issue in our community
• Email us at security@openproject.com, PGP keys can be found at https://github.com/opf/openproject/security/policy